1995 Cummins Hard Start
 

Thanks for all the help. Some background--1995 Dodge cummins, 120K miles, no modifications, Manual Transmission, 2500, owned for 5 years.

Always had trouble with losing power, shutting down for no reason. It may run fine for a couple of weeks and then act up. When this happens it is hard to start, but once started it usually runs OK for a few days before happening again. No one has been able to fix it. Replaced, lift pump, shutdown relay, shutdown solenoid working fine and has not been replaced, replaced fuel separator 3 times over the past 5K miles.

3 days ago I noticed that I had to snap the throttle to get it to start which I have never had to do unless it was really cold outside. Today, I have to hold the throttle down 1/2 way, cranks for 20 seconds, finally starts, have to pump throttle to keep running, won't idle at all.

anyone have any suggestions?? I read that I should check fuel pressures, anyone know where I can get a gauge kit with the right fittings?? Any help would be appreciated. or If you know of a shop in the Charlottesville, Harrisonburg VA area I could tow it there. Thanks

It sounds like you are getting air in the fuel from somewhere. Maybe a cracked fuel hose If it is a leak in the hoses it would have to be before the lift pump because pressure would make a leak obvious. It could also be the IP going bad. Is your oil level going up? That would indicate a bad seal on the IP shaft. Our 92 has over 1.2 million miles on it so with reasonable care yours should be good for a very long time.

Lets start at the simple things first,

When it does run good - what does it idle at?

I think Gradyc is right on the money. Fuel hoses will dry out and develop tiny holes in the hose - lets air in causing you to lose prime but doesnt leak fuel . I would look at replacing all is the fuel hose - and make sure you use hose that is diesel rated. 3/8" supply and the return is 5/16".

That or the injector pump might be dying - but 120k shouldnt kill the Million Mile Pump.

To check fuel pressure you pull the banjo bolt on the inlet of the injector pump and drill and tap it 1/8" npt. Get a couple of 18" grease gun hoses, a 0-60 psi guage, and a needle valve. You need the needle valve or the pressure pulses from the injector pump will kill the guage in a matter of minutes. I now see that you have already replaced the lift pump - so there is little need to check fuel pressure (but it couldnt hurt).

Have you ever replaced the overflow valve??

It usually idles around 800 when it does run.

Air in the system causing it to shut down makes sense. Do you think that air in the systems could be causing my current problem? (Will barely start with throttle pushed 1/2 way, wont idle)

What is the overflow valve? How do I check it and what systems can it cause??

Thanks

updates??

Thanks to everyone that has given input.. Here is a step by step of the work done.

I ordered a fuel gauge and banjo with a needle valve to get fuel pressure. I installed it on the input of the P7100 and I could not get the pressure above 4PSI. I then decided to open the bleed valve on top of the fuel water separator and all I got was air bubbles ( As I pushed the primer bulb a lot of bubble came out of the bleed valve). I figured it must be sucking air from somewhere. I then disconnected the supply line (metal flexible under the truck next to the engine compartment) and I stuck it in a gallon of fuel. I was able to prime the engine and the gauge came up to 14 psi with just hand priming. I then started the engine, it ran for about 30 seconds and I was out of fuel so it cut off.

I concluded that I must be sucking air from between the tank and the flexible line. I dropped the tank this week end and found the rubber hose off the fuel module to have cracks in it. I can hold my thumb over one end and suck on the other end and it pulls air thru the cracks.

I think I have found my problem.. or at least it is a problem.

I now have some quick questions which I will put in another post..

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Does anyone know where I can buy some rubber fuel lines to put from the tank module to the metal fuel lines running on the frame of the truck? Do I need anything special or will just regular rubber fuel lines work. I have read that diesel deteriorates rubber and I really don't want to do this again. Also, the metal lines are rusty. Would it be wise to replace them? I guess I could only get them from the dealer.

It seems to me that the whole fuel line system is a weakness on these trucks. The system has several joints, goes from metal to rubber several times, the flexible metal lines at the cab has rubber o rings.

I am temped to just go with rubber from the tank to the engine and do away with all the joints. Does anyone have any suggestions or maybe somewhere I can get what I need without going back to the dealer.

Also,
The fuel gauge doesn't work so now is a good time to replace the sending unit. Anyone have an idea of where to buy an after market sending unit? The tank module appears to be in OK shape. (The screen filter on the bottom looks OK with no tears) Has anyone seen an aftermarket tank module. If it did not cost me my right arm I would consider just replacing the entire unit.

Thanks for any help.

Most of the hose from the auto parts stores are compatible with the fuels on the market now You could get hose designed for fuel injection because it is a little heavier duty. They also have repair fittings for the feed fittings. Steel brake lines can be used to replace the steel line sections. Some tank units are available from auto parts stores but the best thing to so is ask them when you are getting the hose if they can get it for you. Some junkyards also sell used units now.

We rarely see a failure in anything but the rubber lines with the exception of some around the pump and injection pump. I would replace the connector hoses (rubber) and try it that way first!

I finally got it back together. I decided to go ahead and replace the metal lines that run along the frame and also the fuel module. I figured since I already had everything apart I may as well replace these lines. (The old ones were real rusty). The new lines are stainless so I hope to not have any other trouble with these and also, they came with new rubber ends that fit on the fuel module. (The same type rubber that is on the lines in the fuel module). I started the truck this afternoon. At idle it carries 15-17 PSI. (It does fluctuate a little bit), and at 2500 RPM it carries 27 PSI. I feel like this is a little bit low, but maybe it is ok.

One quick question. My gauge was connected at the input of the injection pump. Is it normal for all pressure leak off to zero after shutting the truck off. I wasn't sure if it should hold any pressure at this location?? Thanks

Most people simply eliminate the steel fuel lines and run hose all the way from the tank.

You are still having pressure issues. Replace all flexible lines that you can. Feed is 3/8" and return is 5/16". Make sure you get the little 4" long return line - the red one in this pic:

Attachment 51270

Try to get diesel rated fuel line - the best stuff is marine rated. If you use regular fuel line, you may be doing this job in the not so distant future - and its not a fun job (as Im sure you already know).

If that doesnt help your fuel pressure (yes its still a tad low), I would look at the overflow valve (on the outlet of the pump - at the front). Be careful not to loose the sealing washers if/when you remove the overflow valve. If youve never replaced this - pick one up.

It looks like this: http://www.tstproducts.com/overflowvalvefor59cummins.

Other than that....you might need a new lift pump. How many miles does yours have? Its not that common but they eventually wear out. But I would look at replacing that last since its the most uncommon failure and its also the most expensive fix.

I still think youre getting air in the fuel system. Maybe at the prefilter/heater? This is a common place for air to enter (sorry I forgot to mention it before). Many people remove the heater unless they live in very cold climates.