I'm running a 1990 5.9L 1st gen Cummins that been having fuel issue of late. Three times now the engine loses power and sputters to a stop and won't restart. My only option has been to tow it to a mechanic. Here's what's been done to diagnose and potentially fix the problem so far.

• Both filters (engine and secondary) replaced
• Fuel pressure checked - nothing wrong
• Fuel pump check - nothing wrong
• Kink in fuel return hose found and repaired
• Injector pump checked - nothing wrong (a 40HP fuel pin and 3200rpm governor spring were installed a while back)

Both of the mechanics who have looked at the engine and fuel system say that nothing they found would have caused the truck to stop working as it has. In other words, they don't know what's wrong and so now that the truck's running fine, I'm not comfortable taking it on long trips.

Having done some research on this, what makes the most sense is that the fuel cut-off valve, or the relay that controls it, is intermittently failing, stopping fuel from getting to the injector pump. As far as a know, the valve and relay are original to the engine which is now almost 30 years old.

Appreciate any feedback about what might be causing the fuel issues and/or best ways to see if indeed it's the valve.

Thanks,

Michael

 

Generally a fuel shut off solenoid won't give you a warning. It just quits. A quick remedy to this is to take off the solenoid, remove the plunger and spring and re install the solenoid. you will have to shut the engine off with the mechanical shutdown lever on the side of the injection pump. you can hook up a cable to the dashboard and just pull it out to shut down the engine. If you have a manual transmission it would be wise to use a locking type cable so you can lock it out. Otherwise, if you parked it in gear and someone bumped into it there's a possibility it would start and take off. Or you can park it in neutral if your parking brake works.

 

Forgot to mention that this effectively eliminates the solenoid and makes your fuel system completely mechanical so the engine will run with the key in the off position. If your truck still shuts off, you can rule out anything electrical I.E. fuel solenoid, relays and such. I would then look for maybe an obstruction in the fuel tank possibly blocking the pickup tube on occasion. Good luck.

 

Thanks for the feedback. I considered this by am not much of a fan of the manual shut off route. I did get a new solenoid and relay which I hope to install soon once the weather improves. Both are original and thus nearly 30 years old. Beyond that I can't find any other reason so far why the gine would just quick like that so I'm fairly confident that I'm on the right track.

 

Sounds like you have it under control. Been driving tractor trailer almost 37 years. At one time mechanical shutdown was all we had. I know the solenoid and relay are pretty short money so it can't hurt. Being 30 years old it is cheap insurance. This is why I stick with my 1st Gen. New ones might be nice and have all kinds of power but at what price? Don't need computers and sensors to get 23 mpg. 160 hp and 400 ft lbs it plenty for a daily driver and occasional work horse. Good luck.

 

Well, I thought I had it under control. When it died again last week, I wiggled the leads to the fuel solenoid and it started up again. Thinking the issue was not the solenoid itself but perhaps the electricity going to the solenoid, I checked each lead (not sure why there's two) to make sure they come on correctly with the key in on and then crimped new connectors and zip tied the one that is most important for ignition into place. But then it died again yesterday. Strange thing of late is that it will not start for a while afterwards but then start (after a bit as fuel reaches the system) up when I think I might have to call in a tow. I did test a spare solenoid I have to see how they work (very simple) and tested the one in the truck and heard it click when a charge was applied directly to the lead.

I guess I could do the following now:

• Check to make sure that electricity to both leads is consistent and normal. If not, redo those leads - which will be interesting since they dive into the harness and I'm not sure where they terminate - maybe my Dodge mechanic's manual will help with that.
• Replace the solenoid. It couldn't hurt but getting it out looks to be a major pain.

Can fuel issues like this come from having replaced the original fuel pin and governor spring with upgrades for more horse power? The issue only began after that upgrade was installed. I've never had an issue like this with any truck I've ever owned.

Maddening.

 

Since I posted this thread last year I've had many cases when the truck dies because of an ongoing fuel starve issue. Apparently I have what looks like at least three different ways the truck gets starved of fuel.

1. Water in the fuel system which is easy enough to fix with new filters and bleeding the system.
2. A faulty fuel solenoid valve which I have deactivated and replaced with a manual shutoff control.
3. Excessive back pressure in the fuel system caused by a non-vented fuel cap (which I replaced with a vented version) and now something where when I opened my secondary fuel filter system (under the truck between the tank and engine) a "whoosh" of air came out.

To get the truck running again, I manually bled the file system via the fuel filter on the engine and then again at the secondary fuel filter until all I saw was clean diesel. After that it started right right up and I drove it home.

But I have yet to figure out how so much back-pressure was created to fuel starve the system. Diagnosing air in the fuel system seems to be a several step process (one mechanic said they tested it but clearly didn't do a good enough job) and I only have so many tools to do a comprehensive job.

So, does anyone know a sure fire way to diagnose how that much air can get into a fuel system and/or does anyone know of a really good, old-school diesel mechanic in the Boston, MA metro area?

This issue is 3+ years old now. I've done and spent so much money on this that while all the work has made several small improvements to the truck, it remains unreliable given I never know when it will stall and what is the definitive reason for it doing so.

Any and all help appreciated.