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Drives great and suddenly dies

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Moose33

Moose33

Jedi Hopeful
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hi all. despite my previous post on the heater core (which is now bypassed), I have an issue I hope you can help with.

Today marks the first day I was able to drive the car out of the neighborhood and not have to push her home... But, she ran great for about a half an hour then while cruising at 60 I lost engine power.
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The electrical didn't flicker so I want to assume it is fuel related (aftermarket facet low pressure w/out fuel regulator). it didn't quit altogether and I was able to limp home firing on 2 cylinders and the accelerator half-way to the floor.

I let it sit for about 5 minutes, turned the key and she runs just as she did at the start of the trip (wonderful).

I know it is not point related b/c I have the pertronix installed. I'm going to check fuel flow and for a stuck carb float in the a.m.

anything else I should be looking at? has this happened to anyone else? and, is there a specific amount of fuel pressure that I should set my B at? (like 1.5 psi for example)
 
Well... until you said you had the Pertronix I was going to say look for wear on the points. Since you could stumble home at reduced speed I'd say you're correct to look for fuel problems. Don't forget to check any fuel filters you or a previous owner may have installed. Take the top off the float bowls (assuming these are HS carbs) and make sure there isn't a wad of scuzz or water in the bottom. I have heard of coils failing when they overheat and recovering at lower speeds but I'd hold off on looking at the coil until you've checked the entire fuel system. As for fuel pressure, if you're running a standard setup I'd expect something between 2.5-3.5 psi would be OK. If this hadn't come on so suddenly at 60 mph I'd also advise you to make sure your air filter wasn't severely blocked. A friend of mine had a totally plugged K&N cone filter that choked off all his power.
 
I vote for carburator malfunction. This could happen for two reasons which are diametrically opposed. If one carb is either flooded OR starved the engine will act as you described. I lean toward the flooded condition as it is the most recent problem I have had (both with HIF's and HS4's). Clean the float chambers and needle/seats and change the filter. Bob
 
How new is your fuel tank? I've seen some pretty nasty stuff in the older tanks and sucking some of that into your fuel lines, new pump, filter ... and hopefully not carb would cause the exact problem you described.
 
Doug- thank you for the quick reply! air filter is not an issue, don't have any at the moment but good idea to look there (future note)

Bob- thanks for the input on the carbs. I've got the HS4's btw.

Rich- the tank is as old as the car. But, I've got a fuel filter before the fuel pump and one in the engine compartment.
 
Two thoughts. First is a vaccuum leak causing Carb freezing, or fuel filter blockage. I read that you have filters front and rear, but have you checked them?

You know, this sound like that old stunt we used to pull in high school with a ping pong ball /ubbthreads/images/graemlins/grin.gif.
 
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Rich- the tank is as old as the car. But, I've got a fuel filter before the fuel pump and one in the engine compartment.

[/ QUOTE ]

I bet you will fix the problem if you remove the rear filter or move it to AFTER the pump. The low pressure pumps have even less suction pressure and even a tiny bit of interfernce will starve the carbs.

The symptoms you describe are all to familiar to gas starvation. Cruising at mid RPMs for a period of time, the pump cannot keep up with the demand and it slowly starves. It could also be something in the tank, but removing the filter will identify the source of the clog...or at least spread it out into the rest of the gas lines /ubbthreads/images/graemlins/frown.gif

It is supposed to be a beautiful weekend...I would drop and clean the tank, filter and pump, then go for a nice ride to see what happens /ubbthreads/images/graemlins/grin.gif

Good luck

Bruce /ubbthreads/images/graemlins/cheers.gif
 
Also, be sure your fuel tank is venting properly. If not, the fuel pump pulling a vacuum on the tank could cause a problem like this. Next time it occurs, immediately remove the gas cap to check. There should be no pressure differential between the tank and the atmosphere.
 
Since you know you've got a filter between the tank and pump, and since you know the tank is original... I'd certainly start by looking at/replacing that filter. I had a Toyota years ago that "suddenly" wouldn't go over 45 MPH because of a plugged fuel filter. I had nearly identical symptoms to yours.

BTW, if you have no air filter at all, get one. Dust and dirt will play heck with your cylinder bores very quickly. I hope you get it sorted out this weekend!
 
Thanks everyone, I really do appreciate the advice and will be trying a variety of things over the next few days.

hope you all have a great weekend and get to get out and drive a lot! /ubbthreads/images/graemlins/laugh.gif
 
quick thought- I took the fuel filters off and reconnected the fuel lines and put the end going to the carbs in a 2 liter bottle. in 30 seconds, less than half the bottle got full. could this be (a) crap in the tank not allowing fuel out and/or (b) a faulty fuel pump??

btw- niether of the filters were clogged.
 
Guy,
If I read you correctly, the pump is free flowing a bit less than two quarts per minute. This calculates to around 30 gallons per hour. Since a 150 HP engine should require about 12 gallons per hour (less for a smaller engine) at maximum power, the 30 GPH should be way more than adequate. Just for drill, try it with all filters in place & just one connection open at a carb.

As a note, the average engine will consume around 1/2 pound per horsepower/hour.

Brake Specific fuel consumption
The range is from .35 to .6 lb/hr/hp. Average is about .5 lb/hr/hp

Gasoline weighs 5.6 to 6.5 lb per gallon. Use 6.0.

Example: 150 hp engine, .5 lb * 150 hp = 75 lb/hr
75 lb/6 lb/gal = 12.5 gal/hour.
D
 
I agree with Dave, that flow sounds adequate. However, as mentioned, your flow tests need to include everything that could restrict the flow (filters, hoses, etc.) Keep at it. If it doesn't turn out to be the pump and filters, take a look at the float bowls carb needles.
 
I made a mistake in my earlier posting.. I said I used a <u>2 liter bottle</u> and I meant a 20 ounce bottle (sorry, was in a hurry).

Dave- thank you for the equation, now I have a little bit better understanding of how to calculate the consumption rate.

Doug- do, or have you had any knowledge/expierence with Grose Jets for the carbs? I don't have them installed yet, but was already thinking about it prior to this little fuel issue.

and, if everything was working right, would there be any point in installing a fuel pressure regulator (having the Facet low volume pump already in place)??
 
I have Grose Jets in the Mini. I have had mixed experiences with them. One of the two I installed was a leaker and had to be replaced. The second one has performed much better. When they work, they work well. If they don't work they're like having worn out old float valves. I'd like to think my experience is the exception not the rule.

Don't forget that when you put any new float valves in the bowl covers you've got to check and reset the float level. This is typically done by removing the bowl lid, flipping it over and measuring the gap beween the lid and the float arm. Drill bits are good measuring tools if you have a set of number drills. Check your manual for what's right for an MGB. I think it's supposed to be a gap of 1/8" for HS2 carbs.
 
[ QUOTE ]
I made a mistake in my earlier posting.. I said I used a <u>2 liter bottle</u> and I meant a 20 ounce bottle (sorry, was in a hurry).

[/ QUOTE ]

Tha should still give you 15 gals/hour, well above the 12 gal/hr calculated at 150hp.
 
I let it pump out about a gallon on Sunday (into a container) and I noticed that every few seconds or so I noticed it was alternating between solid stream of fuel, and a bunch of air bubbles then back to fuel, etc. etc. I'm willing to bet that this is a majority of the problem. It probably wouldn't hurt to run new lines/fittings while the tank is off also.

thanks for everyone's input.
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The air bubbles would indicate a leak somewhere on the suction side of the pump. This would likely show no external drips since there is very little pressure on this side. An unlikely possibility would be vapor lock if it only happened when things are very hot.
D
 
Hello i have been having the same problem with my 70B. I was wondering what the outcome of your problem was. I had the fuel filter changed,the fuel pump and carbs were taken apart and were free of debris and the venting was checked. It ran good for about 200 miles than started doing it again. Similar problem only i cut right out and had to restart, sometimes it took time before it would restart, then it would run fine for a few miles then cut out again.

Thanks

Bern
 
Bern, one thing you may want to look at is the low tension lead in the distributor. These get frayed, or actually separate, and will cause intermittent problems exactly as you describe. The lead is the one that slides into the distributor, attached to the plastic piece.
Jeff
 
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