Problem with a Ford.

[CumminsPower98]

I am working on a customer's '90 F-350 with the 7. 3 Diesel and an ATS Turbo. I am having starting problems and suspect the fuel system. A few weeks ago I installed new glow plugs, new fuel return hoses at all the injectors, and new o-rings that seal the fuel return fittings at the injectors. None of this helped it at all. Even on a hot day if it has been setting for a day or even a few hours it's very hard to start. Today we had temps over 100º and it still didn't want to start so I plugged it in to warm it up some more and finally got it going. It started rough like it had some air in the system. I replaced the rubber fuel hose at the fuel lift pump at the front of the engine thinking it might be letting air in. I will find out if this helped at all when I try to start it in the morning. The thing runs just fine out on the road after getting it going initially. I also pulled the main fuel supply line off at the filter to see if it might be bleeding back but it was full. If there is anyone out there that knows these things please give me some tips if you can. This is the first one I have ever worked on so I don't know a lot about them.



Thanks,

Mark

 

[Scot]

What you describe is the way my 6. 9 injector pump died.

 

[Evan A. Beck]

I work on these things all the time... There's a few things that could be going wrong... I doubt its the injection pump... They usally just run crappy when they are dying, rather than a hard start condition. Here's what I think is going on with the '90 you are describing... The diaphragm in the lift pump will deteriorate over time, causing the susyem to bleed down, resulting in a hard start condition. Put a clear line on the output side of the lift pump, and run it up to the fuel filter head. Start the truck, get it warmed up, and then let it sit. You'll probably see an air bubble within a half hour or so. Keep an eye on it, and see how big it gets. If all the return lines are ok, I'd go ahead and replace the lift pump.



Another possibility is the little fuel pressure regulator on the fuel filter head. I have seen the check valve go bad many times, allowing the whole business to bleed down within minutes.



Also, the shutoff solenoid on the top of the injection pump could be going out. They are easily replaced.



What is the fuel pressure at idle? Under load? Should be 4-6 psi at idle, and not much lower than that under load.



Let us know what you find.

 

[CumminsPower98]

I don't know what the fuel pressures are, I have not checked it out. Thanks for all the ideas I will give those a try. I almost replaced the lift pump yesterday. Even if it's not the problem it can't hurt.

 

[DT]

I agree with Evan, but if none of that helps, there is another, smaller, "charge pump" (takes fuel pressure to 70 or so psi) in the tailhousing of the injection pump... it has been known to go out before. It's not actually the pump, there is a little check valve in there that holds pressure when the engine is shut off, sometimes it will get a piece of junk in there, or get scored, and the thing will be hard to start after sitting for a while...

just a suggestion...

 

[CumminsPower98]

Thanks a lot for the replies guys. I decided pass this one off on the local Ford dealer. I don't have the time to deal with it right now and I would be doing a lot of guessing when it comes to replacing parts.