Engine stalls just after starting hot or cold

[wwheeler]

My '68 M130 has had a problem for a few years that I have been living with but want to fix. The engine will always want to stall immediately after it fires either hot or cold. The engine starts in a reasonable amount of time and then will want to die or run at a very low RPM unless I press the throttle to keep it going. Once passed the initial starting stall phase just after the starter is released, it will NEVER want to stall again and runs well.

I am going to check the spray at the cold start valve but I am pretty sure it is OK because it has been recently rebuilt and I checked the spray then. And besides, it stalls even when it is hot and the cold start is inactive then. I thought about getting the common hot start relay modification kit. But again, it is not just hot starts I am having problems with.

My next thought is the starting solenoid since it activates hot or cold. I have checked that circut and the solenoid is working. I know that the solenoid rod is adjustable and that it acts on the pump rack just as the throttle does. Would adjusting this rod to add more fuel when starting do the trick? Please let me know if anyone has done this.

Thanks for your help.

[jeffc280sl]

Wallace,

Sounds like your car is starved for fuel during initial startup.  The cold start valve appears to be doing its job but the fuel volume from the fip is insufficient to keep the engine alive.  Have you checked fuel volume after the fuel filter?  Some of us have a problem starting when warm only. Its been said this may be caused by fuel evaporation in the injection lines due to heat.  This problem could similarly be caused by leaky check valves which are supposed to keep the fuel lines charged.  After enigine shut down open a fuel injection line at the pump.  See what sort of fuel charge is present.  Wait 15 minutes or so and do the same on another line and compare.  Just a thought.

[wwheeler]

Thanks Jeff. The FI pump was rebuilt less than a year ago and my fuel pump is two years old. Hopefully, the problem isn't here. I have not checked the volume but will. I do always let the pump run about 5 seconds before I start it if that matters.

I was thinking about doing a start up test by splitting the linkage at the throttle venturi so that the pedal controls the FIP only (adds fuel only). I would keep the pedal slightly open when starting and see if it doesn't stall. If there is improvement, then I need to figure out how to get more fuel during start up. Of course, if there isn't any fuel in the lines (drained out), that won't work. 

[jeffc280sl]

There are others more knowledgeable that I on the fip.  I hope they have suggestions.  You should not need any changes to your fip if it was recently rebuilt.  Maybe idle setting.  I would continue to look elsewhere in the fuel delivery system prior to changing the settings on my pump.

[Travis71280]

I'm curious about this issue too, I have the same exact issue with mine, just haven't really messed with it since it runs fine after that first initial stall. I'm with Jeff though, it might be the check valves on the fuel injection lines at the pump because I know with mine I have to hold down the cold start button to get the car to turn over. I thought in my case it was just a lean issue but thinking about it, might be because the fuel injection lines havent primed yet from fuel seeping through the check valves which would also cause your car to stall out too initially and then run fine after your fuel lines prime up. Just thinkin out loud. Too bad check valves aren't cheap.

[wwheeler]

I disconnected the linkage to the venturi so the pedal would only add more fuel when starting. Without the air, the engine wouldn't start. I reconnected the linkage and was able to start the engine and it wanted to die as always but I caught it before it stalled. I am not sure that test proved anything. I will try the reverse tonight and disconnect the linkage at the FIP and see what happens. 

The check valves do seem to make sense. But even if I restart less than a minute later, it still stalls. How long would it take for the fuel to drain out?

I think what I need to do is document when it stalls and what the conditions are and keep a log. Maybe then I can put the pieces of the puzzle together. If anyone has any more thoughts or tests I can run, please let me know!

Thanks for everyone's help.

[w113dude]

Hi W,

I had a similar problem with my SE, If you have the same problem with a hot or cold engine, then there is only one thing that will do this and that is not enough fuel, I had a very lean injection pump, maybe one or two clicks! Worth the try.

[graphic66]

Read the owners manual on the proper starting technique. If you hold the key on a couple of seconds after the engine starts it will probably not stall. This keeps the cold start valve actuated while the key is in the start position. On a warm engine hold the fuel pedal at about half throttle until it starts.

[ja17]

Hello Wallace,

Make sure that the engine starting aids are working correctly first of all. If your car is equipped with the injection pump solenoid it should activate any time that the starter is engaged. Also the intake starting valve should activate at certain temperatures during starting.

[wwheeler]

So far, everytime I have started the engine with the linkage split at the FIP and add only air, the engine starts and doesn't stall! Earlier, I tried the opposite and adding just fuel and it wouldn't start at all. It is starting to sound like there is too much fuel when starting. Plugs are a little rich looking with prolonged idle and but are great looking after a spirited drive.

If I lean the idle mixture too much, I always get hesitation when taking off from a stop. What mixture range would need to be adjusted for taking off from a stop?

I will continue to start the engine with air only and see if it continues to do well. If that is the case and my idle mixture is good, what would the fix be?

Thanks for help with this perplexing problem.

[Larry & Norma]

If the linkage is set up ok, timing etc ok then the best method i found to idle tune is to use a CO2 meter. Gunson's work well.

[wwheeler]

Update.

The engine did not stall when I added only air with the disconnected linkage when starting hot or cold. I have since disconnected the wire going to the starting solenoid on the FIP and reconnected the linkage when starting. The starting solenoid richens the mixture when starting either hot or cold where as the cold start valve squirts fuel in the manifold typically only when cold. My goal was to reduce the fuel in the starting mixture both hot and cold. The idle mixture isn't that far off, if at all.

Since disconnecting the lead wire, the engine starts and does not stall. When I connect the wire back up, it stalls again. So I guess the question now is why. In Texas, it is extremely hot lately (100*F) and the engine may not need the extra fuel right now. We will see if it changes when it cools down in four months.

I know that they eliminated the starting solenoid on later pumps and I think because of the improved check valves. My pump has been rebuilt and I wonder if it may have the improvements so that it doesn't need the starting solenoid? Anybody every run across this?