Spitfire Spitfire Fuel Filter

Well, I'm trying to track down a problem in my Spitfire. When the engine reaches about 4000 rpm under full throttle it severely hesitates. It doesn't backfire, or makes noise of any kind, it just starts "missing" and will not rev any higher.

Before I replace points and condensor(which are new) I thought I'd replace the old looking fuel filter.

So, I've replaced the fuel filter in the trunk with a clear model, and am noticing that there is not a lot of fuel in the filter at any given time. Is there anyone out there that has noticed how much fuel is in their filter while the car is running? There seems to only be about a 1/4 of an inch in mine.

Now I'm thinking that the engine might be starved and my fuel pump doesn't work properly.

EVERYTHING in this car works. There are only two problems. This one, and a nagging slight "shake" at idle(which I attribute to the carb needle being pitted - too rich while warm).

New components: rubber in Stromberg, Bosch platinum plugs, Bosch wires, Lucas coil, distributor cap, points, condensor, rotor, fuel filter.

Old components: Fuel pump, needle in carb(pitted), float.

Thanks.


Adam H.
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1973 Triumph Spitfire

Adam, put a timing light on the marks and rev it up to see if the timing keeps advancing, you may have bad springs or you may need to adjust as required. (They all like it a little different). Wayne

if the tank was sealed or old some debris (sealant or rust flakes) could be partially blocking the fuel line either in the tank or filter inlet.
The filter should be at least 5/8~3/4 full.
turn the filter horizontal and see if it gets better because the debris could be at the inlet of the filter not allowing full flow and shake loose.
Take of sample of fuel and check for contamination.
There are ways to check the pump gpm and if you have a Haynes or other good literature it will talk you step by step through the process.
Just my opinion.
good luck

The fuel pump on the Spit is mechanical;that means it PULLING the fuel through the fuel line check the filter flow while the engine is revving.You may see a difference.
;-O.....Electric fuel pumps PUSH the fuel(incidently to much PUSH(pressure)with an electric pump is NOT GOOD!(regulators)? Cheers
PS;Beware This could cause new thread congestion on the forum ;-)

Thanks for the replies. I like the idea of the mechanical pump more for now - on previous vehicles(Jeepster Commando) the electric pump would sometimes hold the float needle open and cause dangerous fuel situations - KISS(keep it simple stupid).

The fuel is perfectly clear, the tank is not rusty. I'm thinking that the 1/4 of an inch of fuel I've got in the filter is not enough. Something's going on there.

Wayne: good tip I will check advance. Car runs well otherwise, it's my daily driver.

The pursuit of happiness continues(good luck).


Adam.
____________________________________________________________
1973 Triumph Spitfire

Well, I'm glad I decided to look under the hood today with the engine running. My fuel pump was leaking on my starter. Darn, I liked the original fuel pump. I'll have to get along with the cheaper one I was able to find locally(made in Canada though!).

The amount of fuel in the filter looks normal, the fuel pump is fixed, I went through the points, dwell, and timing - still the missing at 4000rpm.

Now that I've got all the fire hazards cleared up I can concentrate on the points, condensor and advance weights tomorrow. I'm only getting about 10 degrees advance while revving the engine up to about 3-4000. Can't tell from the Haynes manual if this is normal or not.


Adam.
___________________________________________________________
1973 Triumph Spitfire

O.K. I've replaced the points, condensor, rotor and cap, adjusted timing and dwell, checked all for vacuum leaks, replaced fuel pump and filter. The coil is new, and all wiring is solid. Still the engine idles irratically(stumbling periodically every second or so), and basically cuts out(on seemingly one or two cylinders) at about 4000rpm.

Being an electrician I'm trying to stay cool, but this one is hurting my brain.


Adam H.
____________________________________________________________
1973 Triumph Spitfire

at least your working to find a solution, keep up the good work. sorry i can't give any help, still haven't started my gt6 once, let alone having driving problems.

good luck, and keep her on the road.

I am experiencing the same thing. Radical idle anf Mid loaded RPM hesitation. Ran strong most of this summer, with a rough idle. Now the miss runs from idle to about 2500 RPM and the hesitation is 3000+ when under load.
I just stumbled on to this thread. I too have changed nearly all electrical.

I am guessing that 10 years later you solved it.
Do you remember what it was?

Desperate in delta.
-Paul

+1 on Wayne's reply. You might also want to check or replace the plug wires even though they seem solid. If still no improvement, get out the compression gauge.
Tom

ru4_it said:

...I just stumbled on to this thread. I too have changed nearly all electrical. I am guessing that 10 years later you solved it.
Do you remember what it was?...

Click to expand...

Paul -

'TheAssociate' appears to be no longer active here so we may never know what he found -- but the things he has checked and the suggestions he received are a pretty good starting point for you.

Checking advance with a timing light, checking compression & examining the diaphragms for tears or holes (stretch them every which way with a strong light behind them) are places to start.

As a new BCF member you may want to identify your car and other info as many do not read the 'new member introduction' posts. You may also want to start a new thread specific to your problem as a decade old thread about fuel filters may not get as much attention.

Here is a more detailed list of the things I've done trying to catch this gremlin:

I have a 1978 triumph Spitfire 1500 and I am at a complete loss. I have no idea what could be the cause of my issues.

The major problem I am concerned with is the car recently developed a random hesitation, bucking, and backfire mid-high RPM under load.

It has always ran rich and had a rough idle since swapping to a single ZS 175 CDST from a ZS 150CD. Other than that, the car ran incredibly strong all summer, including two long/hot trips.

In Trouble shooting the major issue, I noticed that the previous owner had removed the resistor wire and ran 12v to the 6v coil.

Here is a list of everything I have done since the problems developed:
New wires.
New plugs.
New distributor cap.
New 12v coil.
Cleaned and lubed the Distributor (Mechanical advance only, no vacuum).
Removed the electronic ignition and put the points back in (and out then in again).
Removed the carburetor, disassembled it completely, cleaned and reassembled it.
Compression test - good (high and consistent).
Leak down test - good (#1,3, &4 mid green, #2 low green).
Checked the timing (was at 12°, set it to 10° after seeing 10° stamped on the distributor).
Sprayed the carburetor, intake and exhaust manifolds with carburetor cleaner while idling, no indication of any vacuum leaks.
I normally run Chevron 94, I recently tried 2 tanks of low grade.
I have since installed a 180° Thermostat (I learned the car was running cold (140° using an infrared laser) found that the previous owner had removed the thermostat).
Temporarily hard wired the coil to eliminate any chance of ignition switch fault.

Since making all these changes, the problem has become consistent and severe. Any advice on troubleshooting would be greatly appreciated.

Desperate in Delta
Paul

Dear D in D -

The one thing in the ignition system I do not see mentioned is the condenser. Can be tested or a thought-to-be-good replacement tried.

Hey Geo. Are you are referring to the condenser on the points? If so, the car exhibited the same issues even with the electronic ignition points installed, So I doubt that is the issue. But I certainly appreciate all suggestions because it may be something that I haven't tested for or replaced.
Thanks again to all for any past or future input.

Well, the problem returned today while returning home from parts parts store with new fuel filter. I promptly pulled over, plugged in my coil hard wire set up that I left there. The problem remained. So I can scratch ignition switch and really anything ignition of the list.
What I did notice was that the clear filter I installed between the tank and the pump had very little fuel in it.
Limped home, pulled the filter near the tank out only to find it caked in rusty mud.
So I'm guessing I have (had) a fuel supply issue.
Interesting to note that although the tank filter was packed, the front filter is spotless. So those metal canister type filters work very well.
I will be removing the tank soon and giving it a cleaning.
Maybe now I can run a leaner needle.

Oh and yes, I am embarrassed to say that I never changed that filter since buying the car. Especially after seeing some of the questionable practices the previous owner had done.

Hopefully your plugged main filter was the source of all the problems. Let us know how the car runs with the new filter installed.

If you are going to use the car regularly, you may want to replace that new metal housed filter with a translucent plastic one instead. Rather than drop the tank to clean it you could just monitor the filter condition and replace it frequently. The debris in the tank should eventually get washed out and collected by the filter(s).

Update 11.2.16.
Once again, thanks for any and all ideas helping me to solve these issues.
Changed the filter near the tank and the car still has the high RPM lean pop. I also noticed the clear acorn filter installed immediately in front of the pump is nearly empty and is normally 1/2 full.
I then plumbed in a pressure gauge between the pump and carb. I'm getting just over 6psi from a stock looking mechanical pump. Also noticed that after plumbing the gauge, the acorn filter is now half full again and no popping at this point.
One more thing I noticed is that after shutting the car down, it took a long time to loose the pressure in the gauge. Maybe that's normal?
Thanks again everyone.

The 6 PSI figure is high. How confident are you in the accuracy of the gauge? If it is accurate, then you certainly shouldn't be having any fuel delivery problems. In fact, you would expect that the pump would overpower the float valve and cause a rich or flooded condition.

Don't try to judge too much from how full an inline filter is. If you really want to focus on the filter, orient it vertically (not horizontally) with the discharge end pointed up. If a vertically mounted filter looks less than full, then you are experiencing a fuel delivery problem.

If your pressure gauge is mounted between the fuel pump and the carb and maintaining pressure for a while with the engine off... that's a good thing. There are check valves in the pump to prevent backwards fuel flow and the carb has the float valve to shut off fuel flow when the float bowl is full. A gauge that shows pressure is being maintained with the engine off indicates that neither the float valve nor the pump's check valves are leaking.

Hi.
Not to concerned about being full, just noticed that when the car lean pops, the filter is near empty. When it's running good is 1/2 full (1/2 Empty?).
The filter is more or less vertical.
I'm at a loss. Maybe it's a blockage in the tank. I plan to clean and deal the tank once the insurance expires.
-Paul

After checking all the "normal" and simple things have you ever checked the fuel lines for kinks or crushed sections ? All the pressure in the world won't push enough fuel through a bad line.