Tow Job

[courtenay]

Beautiful day yesterday - first drive of the season. After about 20 minutes, with car running strong, I stopped at a light, car stalled and while it cranked strongly it would not restart. Had to be towed home. Pulled the lead from the cold start valve, nothing. Checked the AFM, flap moved easily. All hoses to AFM check out OK. I pulled a plug lead to test for spark - there was spark. Pulled a plug and it was dry. Went out this morning and the car started right away.
Any ideas folks? What would shut down the fuel delivery when the motor gets warm yet doesn't seem to interfere when it is cool?

[TX82FIAT]

It sounds like you have correctly eliminated ignition since it cranks well and you have spark. It also sounds like the car was running great and ran well the next day. IMHO is does sound like a fuel issue. The fact that is fired right up the next day may be a sign of an intermittant problem with fuel delivery. It could be something as simple as some debris/particulate in the fuel that has clogged a filter, line, injector. When the car was turned off the blockage released itself. If this is the case I hope a simple fuel filter change eliminates the problem from occuring again. The first drive of the season could contribute to a fuel issue.

[courtenay]

Thanks for the quick response, TX. While this was the first top down drive of the year, the car was started and taken for short drives through the winter - on dry days. I should also mention that I had the problem near the end of last summer when I had take the car for a fairly long drive, stopped at a friend's house for a beer and the car wouldn't start. I left the car overnight, came back the next morning and again, it started right up. Unfortunately it's a difficult problem to diagnose as the car runs fine when it's cool but quits and won't start when hot. And if it quits when I'm far from home - well, you understand the difficulty.

[spider2081]

This is one of those times when it would be nice if there was a fuel pressure gauge in the dash.
Could you hear the fuel pump running when you moved the flap in the AFM??
Next time it happens unplug and re-plug in the temp sensor in the cooling "T" These connections seem to go intermittent quite a bit.

[rebar1111]

You might check the coil and condenser in the ignition system for failure when it gets hot and is ok again when it gets cold.

[courtenay]

It's getting spark when it's hot, so I don't thing the problem is with the ignition.
I'm a bit of a mechnoidiot - how would I test for fuel when this happens? What systems would fail and shut down fuel delivery to the injectors when the car is hot but not when it has sat overnight?

[TX82FIAT]

It may not have anything to do with the heat of the car. The fuel flowing through a common point such as a fuel filter could have particulate in it. The particulate floats around while driving and then at some point clogs/restricts the fuel from adequately flowing. When the car is shut of a good portion of the fuel pressure is released unblocking the fuel restriction until the next time it floats around and gets stuck shutting down the car. Just a theory based on my old 1970 Maverick Grabber that did the same thing many moons ago. It was some dirt floating in the filter that occasionally shut the car down.

[81SPIDERMATT]

I agree with the possibility that it is not heat related as tx82 stated.... and you seem to have determined that you are getting spark .... you stated " Pulled the lead from the cold start valve, nothing" ..what did you pull??? was it the fuel line? and found nothing? as in no fuel squirt or no gas at all ?? ... do you have a inline gas filter before the fuel pump? .. has the tank been inspected for crud ??

if you have a way to check voltage to the pump that would be good to know .... as far as fuel pressure you need a pressure gauge ... they can be loaned out at most auto parts stores ..cold start fuel line is a good spot to attach the gauge... you can even hook it up and run gauge out to where you can see it as you drive.... checking for both of these things in the morning does not mean that you will see the same results when the car is not working.... unfortunately these need to be checked when the car is NOT doing what you want .... I went thru what sounds to be similar situation... if you have an idea how far you drove till it did not restart try making a loop so that you are at home and not broken down far away ....

[wizard124]

Sounds like a fuel pump issue to me, since there is no fuel in the CSV line. Is the fuel tank venting properly? When this happens, have you opened the gas cap? No sucking sounds when you do?

[bradartigue]

Sounds like a weak pump. They can vapor lock at high temps. Well, I don't know if "vapor lock" is the right term, but a weak pump will lose the ability to pump fuel with adequate pressure through the injectors. Exacerbated when warm - but when cold it is likely only running because the ECU is leaving the injectors full on to make up for the lack of fuel.

I would test system pressure, if it is good then move on to something else like the ignition.

[courtenay]

Sounds reasonable, Brad. If I test the fuel pressure when the car is cold and running will it show as being weak? Next question, what should be pressure be?

[bradartigue]

Sounds reasonable, Brad. If I test the fuel pressure when the car is cold and running will it show as being weak? Next question, what should be pressure be?

Yes, pump pressure is constant.

Find the FI diagnostic manual for the correct way to test and the correct pressure, I don't know the system pressure offhand - maybe 38 psi for L-Jetronic? Verify and test.

[aj81spider]

According to Brad's Fuel injection guide (a fantastic resource when I owned a FI spider) the pressure is 36 +/- 3 psi with the regulator disconnected and 28 psi after the regulator.

[4uall]

this might help

Check for spark, if you have spark then check @ fuel pump for
power & ground, if you have power & ground then check fuel
pressure, it should be @ least 32 pounds with fuel pressure
regulator hooked up & no more than 38 pounds. If the fuel
pressure is in spec then the problem is else where. If fuel
pressure is not in spec, check for plugged fuel filter, if
filter is ok, unhook vacuume line from fuel pressure regulator &
check pressure, if fuel pump is good it should read 38 psi or
close, @ this point replace regulator. If fuel pressure is low
with regulator unhooked, replace fuel pump & filter.

http://archive.mirafiori.com/Gener/47461.html

[courtenay]

All helps, guys. Thanks. Fuel system checks next on the to do list.