Starts and runs fine the first time... just don't turn it off of stall it...

[drpbx911]

1984 2wd stock truck that has run fine for the last few years.

My problem first appeared like this - pulled into 7-11 grab a few things come back out and try to start the truck and it cranks but won't fire up. I pop the hood, pump the priming pump and try it and it would fire up - problem solved. (Or should I say ignored?)
This rarely happened until recently it has gotten worse, a lot worse.
It still starts fine in the morning and runs fine until it is shut off. Then it won't start and priming does not help.

Actually, the problem may have been there for a lot longer than I realized but I don't stall my truck or go to 7-11 anymore so when I shut it off it's off long enough to mask the problem. However, yesterday my son borrowed the truck to teach his girlfriend to drive a stick. That's when the problem could no longer be ignored since I had to go rescue them and couldn't get it started for a while when I was with them.

Since then I've changed the fuel filter and installed new fuel lines from hard lines to filter, filter to pump, and pump to return line. This didn't change the problem but was on the to do list and now it's done.

I've looked for information about the pump but only found general information. For instance, there is a fuel shutoff valve that is supplied 12v when operating but removed when key is turned off and fuel flow is stopped. A Bosch video on Youtube shows the fuel shutoff is near the fuel inlet and I found a few wires in that area. I found what I think is the fuel shutoff and wire and the 12v is present when the problem occurs i.e. it still won't start.

If I wait a while it will start and run fine but the time varies. As I was writing this I thought of another test to do - start the truck and let it run a while, stall the truck but don't remove power and this should leave the shutoff valve in the open energized state then try to restart the truck - I did that and it still would not start.

Here's another thing I just tried. I drove the truck and with no cars around I swerved the truck left and right hard to stir up the fuel and shake loose any setiment that might be around the fuel pickup. At first this seemed to help. When I got back I cycled the truck on and off a few times but the problem did return. I can't be sure if this stirring up the tank did anything at this point.

I'd like to try a different fuel source to eliminate the existing fuel, tank and dirt but uncertain how I might pull that off.

I'm running out of ideas here. I'm uncertain if this problem has gotten a lot worse over the last couple days or I'm just more aware of it.
I know this very well could be the beginning of the pump failing but it could also be something simple I'm missing and others have already solved.

I'm looking for somebody who has had this problem and found the simple little thing I'm overlooking and will share their findings with the group.
Besides that anybody else run into this problem or have any ideas?

Thanks in advance.

[skullzaflare]

If the injection pump is failing, you will see simaliar things, though you would normally notice power loss the longer it runs.
Next time it does it, pour a bottle or 2 of water over the injection pump to cool it down, and see if it starts

[drpbx911]

Hello Skullzaflare and thanks for the reply and the suggestion. I did try the water to cool down the pump but got mixed results. I'm certain heat is part of the cause of the failure. When it's cold it starts fine. It only fails once it has been running for a while. It could be I need to get a bigger bottle of water.. :)

Here's an interesting update. Once I warm it up I can stall it by popping the clutch while in second gear and leave the key on - never removing power from the fuel shutoff valve. It starts every time. I think it could be the shutoff valve that's failing. I also monitored the voltage to the shutoff valve and the voltage is the same as battery voltage. ( I'd seen a post that addressed a problem with voltage drop to the shutoff valve - so that could be a source of trouble just not in my case. ) Oh yeah, when I stall the engine and restart I can do that several times with no failures. As soon as I turn the key off and try to start it fails.

BTW, this response has been on my desktop for a couple days and I always had something to add to it so I never sent it. Sorry for the slow response and thanks again.

I plan to try to remove the fuel shutoff solenoid in place and without disassembling too much of the pump. Anybody done this.

I have another question - can anyone tell me what the connection right above the fuel shutoff is? I've seen it on some other documents but none identified it.

Thanks

[skullzaflare]

the 2 pin connector above is a jumper that goes to the Tach wire. The solenoid should come right off, another diesel guy on facebook had to replace his.
Sounds like the solenoid is the failing part. If it cuts off try dumping water to cool just that solenoid. In theory you shouldnt have power loss but complete loss if it fails

[drpbx911]

Thanks for the reply. I think I know which one you're talking about - it's the one that has 2 wires and goes to the right side of the pump. I look more closely at the other solenoid and learned a few more things. The solenoid I'm uncertain about is right above the fuel shutoff solenoid and that would be the rear of the pump. The FSS screws down and has a single threaded lug in the center that is pointed straight up. My mystery connection looks very similar but goes in from the rear and screws forward and there is a single center lug that is pointing to the rear of the truck. I will try to attach a picture. This solenoid is the same diameter as the FSS but has something to do with the supply fuel line, the return fuel line and returning fuel line coming from the injectors. In addition to the fuel lines the 12v power goes through a plunger switch activated by the throttle linkage when the throttle in depressed 3/4 or more and supplies 12v to this solenoid. This must change the routing of the returning fuel but why does the supply fuel run through this as well? Thanks in advance.

20920

[drpbx911]

20923

This is a better picture. You can see both solenoids and most of the plunger. Ignore the wear marks on the vacuum line that will be replaced. The mystery solenoid is powered by voltage from the plunger when the plunger is pressed by the throttle linkage to the 3/4 or more position. In the previous post you can see the plunger "button" but not the FSS. Thanks again for any information you can share.

[givememelon]

I too have this problem. With my 89 Ram 50 2.0L
First off, feel free to correct any of this info I'm about to spill.
Mostly occurs after driving across town and idling in traffic too long, ie when the engine is hot. I talked to Weber cause I just installed one of their carbs. They tell me it is a flooding issue (not sure i understand the basic flooding concept) caused by a either improper tuning, and miht have to do with a vacuum leak. He said you can test for a vacuum leak by running the engine and turning the mixture screw in all the way. If the engine still runs, there is a vacuum leak. Sorry if that's common knowledge.
Anyway I replaced every cracked line and gasket, and plugged all the ports. It runs better, and I can get the mixture screw in range, but still the engine runs when it's all the way screwed in. It happens less often, but after lots of idling it still stalls. I took it to a shop this week (for the first and last time) hopping they could settle it. They did find and repair a vacuum leak. And that is ALL they found. For $120. They did also re-tune the carb. Of course they tell me she is good to go. Alas, it stalled on my way home from the shop (perhaps related, perhaps another issue entirely) while i was gassing to get up a hill. It did start up right away, but I have not been able to drive it enough to know if the hot start stall is still an issue.
This may have been an issue before the Weber too. I did have stalling problems then but it's definitely gotten worse.

[skullzaflare]

Well if he has a weber, or a carb in general on his truck, thats the source of his problems! lol

[geezer101]

^post needs to be moved to a happy place :)