View Full Version : Fuel or Spark Issue?

01-21-2007, 11:31 AM
I have gone back through the Search engine and I am still having trouble determining the fastest and easiest way to distinguish between a fuel startvation issue and an electrical issue.

I am pretty inexperineced with working on TR's (I prefer the driving experience vs. the mechanic experience), so bear with me as a describe the situation. You may recall recently that I had complained of my 61 TR3A running rough. Well, it finally died. Let me describe it.

For a while it was running as if it was being starved of fuel or that it might be misfiring (I find it hard to tell the difference). Recently while I was driving, it really got rough (jumping and jerking quite a bit - felt like I was running out of gas, although it is full), so I turned around to head home. It finally died. I got it to start again, went about a quarter mile and it died for good. Had to get it towed home (a measily mile - yea AAA!).

Current symptoms are that it will just crank, but will not fire. I would think electrical, but I find it weird that it died on me, then I was able to start it, then it died again. Electrical things (in my mind) either work or they don't. Fuel / mechanical things can "sort of" work as they go from the working to failure modes.

Things worth noting. It does smell like gas after I crank it a while. The fuel filter does have gas in it. It looks pretty clear to me. The choke appears to be working, at least on the surface the mechanism seems to be doing what it should. the car is negative ground. My coil has + and 1 on it and the - goes to the points (which I think is correct). Nothing "looks" wrong in the distributor cap (we will hook up timing lights, dwell meters, check resistances and voltages later today).

Anyway, long story short, I have a neighbor who is willing to help, but I want to try to eliminate things as fast as possible. If this was your situation, what would you check, how would you do it, and in what order?

A huge thanks in advance for your help.


01-21-2007, 11:41 AM
Bryan, if you smell gas and it won't start, it most likely is an ignition problem.
Pull a wire from a plug, hold it about 1/4" away from a good ground, and crank the engine. You should have a bright blue spark jump the gap.
That would be my initial test, anyway.
Make sure the points haven't closed up, as they often do.
Keep us posted, and we'll have you back on the road in no time.

01-21-2007, 12:10 PM

when you pull that spark plug after a non-start,
check it to see if there is gasoline on the tip.

Then follow Jeff's advice. If you have a spark make
sure it is a good strong, blue spark.

My car breaks a lot and will not start many times
from blown up coils. I get a weak, dim spark when
my coil needs to be replaced.

So look for a strong, blue spark. A dim spark could
be a bad coil.

How long has your fuel filter been on the car?
They are cheap. Couldn't hurt to replace it.

best of luck


01-21-2007, 12:50 PM
Just about to head out and work on it. Just another FYI. The car was sitting for quite a while until about a year ago. When I got it running again, we did drain and inspect the tank. loked good. We also blew out the lines and replaced the fuel filter. I'll let you know if I get a spark. If the coil is bad, can it go bad "over time" or does it just die? As I said the car was running poorly on and off before it untilmately died. Could taht still be a coil. If I do not get a spark, how do I distinguish whether it is the coil or something in the distributor. I assume I can measure resistance or voltage across the coil. Correct? What should me readings be?


01-21-2007, 12:53 PM
My car breaks a lot..

This struck me as funny. Probably a common comment in this forum.. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

01-21-2007, 01:15 PM
I'm a trial and error guy with (maybe) too many predilections.

Someone on this Board recently solved problems by installing a new condenser in the distributor. It first goes without saying that before you do anything with a rough running TR, you make sure you have good points, condenser, the right point gap, and accurate static timing.

So, check that first.

Then, with the key on, make sure you're getting current to the coil and from there to the distributor. Like others have said, a good test is to have someone crank the engine while you're holding a plug wire a short distance from a ground. See if you're getting spark. Make sure you're in neutral and you don't start the car up!!

Because you said the car runs and starts, or vice versa, two things immediately come to mind. Your fuel is obstructed or you're losing spark while you drive. The latter in my opinion is rare, but I suppose it could be a bad wire or connection, or bad coil. For me, over the years, it was almost always the fuel--dirt, junk in the tank, etc. Also, I'd rather run rich than lean, so be sure your mixture is right and that you're not starving the engine of fuel.

I don't like recalling this, but after many experiences with a stalled '62 TR, I finally disconnected the gas line where is goes "into" the fuel pump from the tank. It dribbled. It should have flowed strong. Problem: a nice piece of scrap wood furring someone dropped into my tank years earlier.

Good luck, and now that I've rambled, let us know what the real problem was!

01-21-2007, 01:18 PM
Meant to say: Don't underestimate the importance of a good distributor cap, rotor and plug wires. I've been stuck because of those, too. It's embarrassing to be towed to the shop just to replace a simple distributor cap.

01-21-2007, 01:59 PM
Because you said the car runs and starts, or vice versa, two things immediately come to mind. Your fuel is obstructed or you're losing spark while you drive. The latter in my opinion is rare, but I suppose it could be a bad wire or connection, or bad coil.

Good luck, and now that I've rambled, let us know what the real problem was!

I just went out to tackle this thing and thought "why don't I just give it another try before I do anything", and "Voila" it started. So I thought, "What the heck?!?!" The only thing worse than a broken car is an INTERMITTENT broken car. It is always a problem to make the problem reoccur.

Well, I guess I got "lucky", while I was revving the engine (it had already got to running temperature, and I had driven around my cul-de-sac a bit) it died again. I restarted it and it died almost immediately. Now it is back to just cranking. The fuel filter is EMPTY and fuel IS NOT flowing into the filter when I crank. Just the occasional dribble.

OK, so here is my latest issue, since it did start, I am thinking clog in the line. The glass bowl in front of the fuel pump is FULL of gas, so it seems to me it is the pump or a clog in the pump or in the line after the pump. I guess the pump could be bad, but wouldn't that NOT be an intermittent issue? Wouldn't it just either work or not work?

I guess I can check the flow of the fuel prior to the pump by removing the line and seeing if it just flows out. If it doesn't, there is a clog. The major pain in the rump is that I filled the gas tank the DAY it originally died. It is completely full. Annoying. I guess I could clamp off the line once I see that it is flowing.

Any thoughts based on this rambling information?

01-21-2007, 02:09 PM
Well, Bryan, you can start by disconnecting the line from the tank to the pump and see what kind of flow you have. If that looks good, disconnect the pump to carb line, remove the coil wire at the coil, and crank the engine to see what kind of fuel delivery you get.
Sometimes a gentle shot of air in the line from the pump back to the tank can dislodge any blockage, but that doesn't cure the problem. If there is a blockage in that line, and you blow it out, chances are it will find a way to return.
Have a fire extinguisher handy when you do this, please.

mike crane
01-21-2007, 03:16 PM
I had a similar problem with my TR6 and we had a TR4 come to a halt on a road trip last summer. After a lot of head scratching and checking for spark and gas flow we found in both cases that a falwty (take note Basil)
rotor was the cause. On mine it was all the more baffling because it was a nearly new rotor (Lucas) and showed no outward signs of being defective. It is still running on the used replacement after a 1500 mile tour. I am running with a Pertronix so I knew that it was not points or condensor related. My first clue was when I pulled the pertronix and reinstalled the points and it still wouldn't run. When the TR4 stalled on our tour the first thing we did was install a replacement rotor and all was well the rest of the trip. Your results may vary, but try it.
Mike Crane '71 TR6

01-21-2007, 04:13 PM
Some additional stuff,

There's a brass screen at the top of that glass bowl on your fuel pump you may want to clean first, then replace, then check fuel pump for proper operation as Bugeye suggests. The screen is in the upper part of the pump bowl housing and may stay in the housing when you drop the bowl so you may have to prise it out carefully as to not distort. You can clamp off the rubber hose of the fuel line with vise grips or a hemostat if your shut off is not there or inoperable. Use something like a rag to protect the hose from the serrated jaws of the vise grips though. Do not reuse the original cork gasket for the glass bowl it will probably leak. You will need to buy a new one. Also check the vent line from the gas tank for blockage from mud wasps. These pumps don't gush out fuel either they just seem to spurt so if it's spurting it's working.

Jim Lee
01-21-2007, 04:44 PM

In your first posting you said that there was fuel in the filter "The fuel filter does have gas in it.". Now there is no fuel getting to the filter but you fuel pump glass is full? I assume that your filter is between your fuel pump and carbs. If the tank is full I think you are almost home with one of two problems. A flaky fuel pump or an obstruction that is on the move between your fuel pump and carbs. I have an electric fuel pump on my tr3a that I got at the local auto parts store for about $20. Less than a carton of cigarettes in North Carolina. I am pretty sure that your fuel pump (especially if original) could be providing enough pressure occasionally and for short periods of time if you had a dying diagphram or bad seal in the pump. My approach to trouble shooting the mechanical fuel pump would be to pick up a 3-5 lb pressure 'Facet' pump at your local auto store and by pass the original pump as the quickest and easiest way to find out if the pump is the problem. Do you know if it is original? Does it have a hand primer on it?

You would probably first want to do the easiest and cheapest
troubleshooting by detaching the fuel line from the pump to the carbs and blowing it out. If that makes no difference than I would pick up an electric pump even if you just use it for troubleshooting...to find out if your pump is bad and
then get another semi-original or rebuild your pump. All you have to lose is about 20 bucks and even if you decide to
go back to the original you will have bought yourself as much time as you want to rebuild or replace. I had an original pump which went bad and it was very inconsistent
until I replaced it. My theory being that under some conditions it was able to provide enough oomph to get the gas to the carbs, and sometimes it was not. I did the electric pump thing and never went back.

Good luck and be sure to tell us how you fix it.

Jim Lee

01-21-2007, 05:14 PM

You are right, I am getting close. I checked the line between the pump and the filter and all is well. Perfectly clear. So I am thinking the pump is bad.

HOWEVER, one new wrinkle. While I was removing the fuel line from the pump to the filter, I noticed that the vacuum unit attached to the distributor was cracked. Actually when I noticed it, I jostled it a bit and it broke further (typical Bryan Monroe move to further destroy something). It looks like the PO (I gotta be careful here, because the PO is my Dad!) rigged it with epoxy or something. The thing clearly is not pulling any sort of vacuum anymore.

Two questions...
1) Could this be part of the problem or did I just create a new issue?
2) How does the vacuum unit attach to the distributor? Mine is so rigged I cannot tell how is supposed to go. The Moss diagram looks like it just slips inside the distributor, but how does it stay in place?

So now I have 2 problems. The vacuum unit and (potentially) the fuel pump.

Gotta love these LBC's!

01-21-2007, 06:10 PM
Let's assume the carb jets are set right and the pistons fall freely when you lift them. And let's assume no blockage inside the fuel bowls.

I'll now pose another idea for you to check. Hope it's not a waste of time. I'll enjoy the typing. Here we go:

The fuel pump bolts to the engine with a manual "flipper" that goes into the block. There's a pin in the pump housing that holds the flipper in place, and that pin can often dislodge and allow the flipper to dangle inside the block. That would mean no gas, no pump operation.

This is not the "red-herring" issue some might think it is. It happens with some real frequency. Take a hard look at the back part of your pump, with a good light, and examine the pin to see if it's protruding or whether it's squarely in the pump housing, equal distant on each side from the exterior of the housing.

If there's a problem, take the pump off and fix it. I did this just 6 months ago. Didn't take all that long. The flipper was literally hanging on the dislodged pin. That pin fits in with mere pressure--or by what might be called a "peening" of the pin ends.

Anyway, maybe irrelevant.

01-21-2007, 06:12 PM
BTW, a cracked vacuum line probably wouldn't have much to do with your problem.

01-21-2007, 06:21 PM
I had alot of the same problems with my car and like kentvillehound said,the new condensor and point gap adjustment has the car running absolutely beutiful. If you haven't already tried this I would be very interested in seeing the result.

Jim Lee
01-21-2007, 06:40 PM
Hi Bryan,

You wrote:
"While I was removing the fuel line from the pump to the filter, I noticed that the vacuum unit attached to the distributor was cracked. Actually when I noticed it, I jostled it a bit and it broke further"

The vacuum on my previous distributor was not working for I don't know how long. It is possible that it could make a difference in how the car runs but it is not going to stop the car from running. I don't have any experience trouble shooting a bad mechanical pump but if there is any way to see a problem WITHOUT having to remove it, like checking for both ends of the pin, you should definitely do it. The only thing that I know of is to check the pressure either by detaching the fuel line from the carbs in a safe manner and actually observing the flow or sticking a pressure gauge just before the carb. But the pressure gauge would probably
cost as much or more as the electric fuel pump at your local
auto store. You could attach some fuel line from the downstream side or the pump and into a proper receptacle and
see what kind of pressure/flow you have. It is not very much but if you get nothing or very little it should be pretty obvious. That would also give you the chance to blow
out the pump to carb line which is not going to hurt even if there is not blockage.

On my 59 TR3A the vacuum line to the distributor is a very small metal pipe like a mini brake line that attaches under the manifold and at the vacuum pod on the distributoe with a
threaded air tight fitting. I don't see any reason why you could not just splice the broken pipe to the distributor using a small piece of hose as long as it is air tight. You
will have a vacuum leak in your manifold if you do not plug it or reattach it. I understand that many aftermarket and rebuilt distributors do not have the threaded fitting.

Jim Lee

01-22-2007, 05:00 PM
Blow compressed air thru the line from the fuel pump back to the tank.

Check all flexible fuel lines...they get soft and collapse blocking fuel flow.

Check all fuel filters...some PO may have installed an in-line filter that may be plugged.

Hook up an "Okie" gas tank and see if the car runs with that...that will isolate the fuel supply and if the car runs OK then you have a blocked fuel supply line.

Oh yeah..an Okie gas tank is a temporary gas can hanging from your hood...hook it up to the inlet side of your fuel pump or the inlet side of your carbs...

01-22-2007, 06:20 PM
Before you go too far, do what YankeeTR said. Blow that line back to the tank. Use compressed air. I'd do that before worrying about new pumps and alternative setups.

Careful. The fuel might really start to flow.

01-22-2007, 08:31 PM
Before you go too far, do what YankeeTR said. Blow that line back to the tank. Use compressed air. I'd do that before worrying about new pumps and alternative setups.

Careful. The fuel might really start to flow.

Even if the bowl just prior to the pump is full? Seems that if there was a clog, the glass bowl would not be full? Am I wrong?

Also, maybe a dumb question, but what the heck. When I take off the fuel line prior to the pump, I will clamp the rubber part of the line with vice grips (I will be careful not to damage the line). If i release the vice grips and fuel flows, can I assume it isn't blocked? If not, how do I blow air into it while fuel is flowing? If you say "drain the tank", that is a huge pain. I just filled the car up the day it broke down. It is completely full!

Thanks for bearing with me on this stuff.

01-22-2007, 08:50 PM
Don't pinch it off. Get a bolt that fits into the hose, and use a small hose clamp on the bolt. Gas in the bowl only proves that some gas is getting through.

01-23-2007, 01:13 AM
Sorry, I meant to add:

You're right. If you remove the line and it's flowing strong, that's probably not the problem and you can just reconnect right then and there. You shouldn't have to drain the tank in any fashion. The only suggestion here is to rule out any fuel line blockage from the line to the tank. Maybe that's not the problem, but, again, if points, condenser, timing and spark aren't the problem, and if it runs but then shuts off, something sounds suspicious about the fuel. Just suggesting you rule that out by checking the pump and the line.

Good luck.

01-23-2007, 07:22 AM
I had the same problem on mine when I bought it and once in a while afterward. I cary a can of compressed air in the trunk with a small plastic tube attached to it. when the car starts to run bad I blow the crap out of the line and it's fine afterward. The more I drive it the better it gets. I haven't had to do it in over a year now.
Mine would run at an idle and then cut out after about half a block. if you let it idle a while it would go a bit farther.

01-23-2007, 10:16 AM
I know a TR3 driver that had fuel starvation issues and after checking thru all the major fuel and spark issues he claimed that the fuel bowl rubber "top hat" type seals were swelling up just enough to block fuel flow after driving for awhile. He says he trimmed a small amount off the top of the seals with an exacto knife and that solved the problem! Anyone heard this? Perhaps a softer type of rubber compound in newer seals??? I had the same issues you describe when I tried to start my 3 after a rebuild...turns out the fuel filter (that I thought I had changed previously) was plugged with bad gas sediment. DOH!

01-23-2007, 11:24 AM
Had a similar problem with my TR6 last summer. Died suddenly after it was good and hot. Checked everything electrical-ok. After the engine cooled, I tried it again but no go. Next day, on a whim, tried it again and it started so I used it to run a few errands. Well after it got hot, and at my furthest distance from home, and on the busiest steet (underpass actually) it quit again. Towed it home and checked the electrical again because it sure seemed like an electrical issue. Tried starting at different times over the next couple of days. Sometimes it would start - sometimes not. Didn't have much faith in it so I didn't venture far from home. Finally switched out the fuel pump and had many trouble free miles for balance of summer. With the old pump, starting was random but when it got hot something would definately cause it to stop altogether.


01-28-2007, 06:19 PM
Well, for those of you who helped last weekend, here is this weekends update. I was so sure last week that this was a fuel related issue, I was prepared to take apart the fuel system today (an even replace the fuel pump if necessary). I checked all the fuel lines today and there is no blockage. I am getting good flow from the pump while cranking. I even checked the flow "after" the first carb by pulling off the line between the carbs and cranking the engine and seeing the flow. It is very strong. Bottom line the carbs are getting fuel.

The carbs also seem to be working right. I did not dig into them very much, but I did check the floats and all seems to be fine there. there is also a good pull on the air side. I took the filter off and good feel very good pull if I put my hand in front of the air intake while I was cranking the engine (that little starter botton under the hood is a savior!).

The reason I was so sure it was the fuel side of things is that the car did run for a while last weekend. If you will recall it had died on me, and I couldn't start it. Then (magically) it fired up. It ran a while and died again. At that point I could crank it and crank it, but nothing. I sort of figured that something was wrong with the pump and that fuel had somehow made it into the carbs while it sat (gravity / equilibrium / something?!?!) and it started and ran long enough to burn the gas out in the carbs. It turn out that I made a bad diagnosis, and the pump seems to be operating fine.

Anyway, I now think the fuel is fine and that the elctrical is where the issue is. I of course have no idea why it died, started, and died again. I tend to think electrical things either work or they don;t so the fact that it started and ran for a while really threw me off.

Today, I checked a couple things electrical. Here is what I tried. Please tell me what your next steps would be. I am not getting a spark at any of the spark plugs. I pulled each plug and tested them by grounding them and seeing if I could see a spark. I couldn't. I also tried to see if I could get an arc from the plug wires driectly to ground (using a scredriver), which I could not. I also tried a timing light on all the plug wires and got nothing. Lastly, I tried the timing light on the coil wire and saw nothing. I am not sure what to check now. I have seen some posts on here that suggest replacing the coil and I have also seen someone suggest the condenser in the distributor. I am not real keen on just randomly replacing things until something works. If there is a good way to hone in on the problem, I would appreciate hearing about it.

Based on my little saga, does anyone have any ideas? My trouble shooting skills are clearly bad, as I was 100% sure it was fuel related last weekend, and I am 100% sure it is spark related this weekend.

I think I am up for one more diagnostic round before I have a flatbed take it to the mechanic. I really want to be DRIVING the car! On the poistive side, I am learning....


01-28-2007, 06:35 PM
Bryan, the first thing to check is that you are getting voltage to the + terminal of the coil with the key on.
We'll proceed from there, step by step.

01-28-2007, 08:39 PM
OH MY GOODNESS!!!! I am an idiot! /bcforum/images/%%GRAEMLIN_URL%%/blush.gif

The + wire on the coil was hanging on by a thread. I had missed it before because the break was under the shrink wrap at the quick connect. What made me notice it this time was the voltage was jumping all over as I touched the meter to the terminal.

Anyway, fixed the wire and it fired right up. Drove it around the block a few times. Ran rough at first, but it was probably bathing in fuel from the 8000 times I cranked it.

When I have another nice day off (this dumb career stuff is getting in the way of my LBC fun!), I will check the adjustments. I messed with so much stuff on the fuel side, it is probably all out of whack.

K.I.S.S. (keep it simple stupid) was never more applicable.

Thanks for everyone's input. If nothing else, you all did a nice job of educating me on the fuel and ignition systems.


01-28-2007, 08:41 PM
Good news indeed, Bryan. Glad we could help. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

01-28-2007, 11:38 PM


Solved. Nailed it.

See, there's always value in experience!

01-29-2007, 05:31 PM
See, there's always value in experience!

It's just a shame it takes so bloody long to acquire! With some <u>not</u> fun lessons along the way! /bcforum/images/%%GRAEMLIN_URL%%/cry.gif