Hi folks,

I'm new here and although I've driven diesels for many years, I'm new to Cummins diesels. I bought a '93 D250 w/service bed last summer, and have been picking away at its problems one by one. It has recently developed a new problem, though...

I had noticed a drip from the water-in-fuel sensor, and had called around and balked at the price of that little sensor, and did not get around to fix it. This was back in January, a very busy time of the year for me... then I was out of town and so the truck didn't get started for about three weeks. I came home and tried to start it and it turned over ok, but would not start. I figured I might have some air in the fuel system, from that drip on the bottom of the fuel filter. Of course it was cold and snowy that week and the hood was frozen shut, I couldn't get it open even with a heat gun, so the truck sat another week or so until the weather warmed up and I had time to mess with it...

I didn't have much time to mess with it, so I ended up ditching the water-in-fuel sensor and using a closed-bottom NAPA fuel filter. I filled the filter with fresh diesel, installed it, cracked the banjo fitting above it, and tried to prime the rest of the air out of the filter by pumping the lever on the side of the diaphragm lift pump. I couldn't feel any resistance there, it sounded like I was pumping air. I tried a few different things and probably pumped that little lever 1,000 times – no luck, just air. I ran out of time that day, and had to leave the truck again...

I asked around, and a friend recommended pressurizing the fuel tank with just a couple of lbs of air, to push fuel to the lift pump. I did this, with the banjo fitting above the fuel filter cracked, and my wife watching for diesel to spurt out. It did after a little bit, and then I was able to fully prime all the air out, using the lever on the lift pump... closed the banjo fitting, cranked the truck over for a few seconds, and it ran fine after that...

Now comes the strange part... I drove the truck on & off over the next week and a half or so... maybe drove it to town four or five times, with no issues. Then, one day I drove to town and turned it off for no more than five minutes (I hadn't even gotten out of the truck), and when I tried to start it, no luck... it was starved of fuel again! I thought I might be low on fuel (it was reading 3/8 tank, and the gauge is a little whacky), so I went and got 5 gallons and put in it. I tried priming it with the lever on the lift pump, but still no luck...

I ended up having to hitch a ride and get an air tank and pressurize the fuel tank again, and once it had fuel through the lift pump, it started right up. I drove straight to the fuel station and filled it, which took 12 more gallons – so 17 gallons total that day, in what I believe (from the measurements of it) is a 30 gallon tank... so it should have had plenty of fuel to begin with, I had not ran it out...

The truck has been parked (slightly nose-down) and I haven't had any time to troubleshoot, so last week I brought the truck to a shade-tree mechanic down the street and asked him to try and find out what's wrong - maybe a leak in the fuel lines, etc... I thought there might be rubber hose sections in the fuel line, and maybe one of those had a pinhole leak, allowing fuel to drain back to the tank? He pressurized the fuel tank and couldn't find any leaks, and says this truck has hard plastic fuel lines from the tank to the lift pump, and the return line as well...

I'm wondering what could be causing this fuel starvation, possibly the lift pump? Do these diaphragm lift pumps leak into the block if they leak? I haven't noticed an excess of oil or thinning of the motor oil. I do not yet have a fuel pressure gauge...

I'm up for replacing the lift pump if that's what's needed, and I see people upgrade to the piston pumps, but I haven't yet read through why or which ones... are most people doing the 2nd gen pumps? In other diesel rigs I've owned (GMC, John Deere, etc.) I have always just installed cheaper (~$60-$80) electric lift pumps, for the ease of priming after a filter change... I'm not after crazy performance, I'd much rather get economy over performance, so what pump do people recommend?

Thanks in advance for any advice,
-N.

 

Yes the lift pump Can and does leak into crank case very easy . I would Change out the lift pump and look up Geno's Garage they have a Load of stuff for First gen truck's and very good Company to deal with along with fast shipping . once the leak is fixed and lift pump is changed let us know if that help's and Also Welcome to The Funny Farm of First Gen Owner's .

Val

 

I had very similar problem like you are having, I was convinced it was losing prime, turned out to be a coincidental loose wire at the fss. A good and simple test is to run 12 volts directly to the fss and see what happens...Mrk

 

Also know that the lift pump will only hand prime if the lever is on a certain part of the can lobe. There is one position where you can pump till your arm falls off and your just going TT in the wind. The VE pump can pull it's own fuel enough to run. It's very possible your lift pump is kaput and causing it to lose prime.

 

Thanks for the replies, guys...

So knowing that these diaphragm lift pumps can and do fail this way, do you guys think I should replace it with the same style pump, or a different pump?

I will check the FSS, I hadn't thought that could be an issue since it's downstream of the filter, but I will check...thanks.

I do realize that the lift pump will only pump sometimes via the manual lever due to the cam lobe... I can feel the difference, and have bumped the motor over the couple of times it felt like I wasn't pumping anything... but it's when I can tell it's pumping and I'm only getting air, that it's frustrating...

Thanks,
-N.

 

When mine quit I replaced it with a low pressure piston pump. I just don't trust that the original style pump won't rupture and fill the crankcase with fuel. To me it was worth it just for peace of mind.

 

Montana, when you say "low pressure piston pump", do you mean something like this?:

http://www.genosgarage.com/REPLACEME.../#.UzIf3mSicTE

Thanks,
-Norm.

 

StorminN,

The pump you found operates at too high of a pressure for the front seal on the VE.

There is a low pressure version.

https://www.dieseltruckresource.com/...ad.php?t=93722

 

What he said, You can change the spring in the 94-98 pump to lower the pressure. 15PSI is about all thats safe for the VE injection pump.

 

Thanks guys,

I didn't realize the difference, now I do. Where do most folks source the (I assume) softer spring? I also see that Oregon Fuel Injection sells a 1st gen low-pressure piston pump kit for $160, does that seem reasonable?

Thanks,
-Norm.

 

Hungry diesel sells springs. The Oregon kit seems reasonable, I assume it includes the hard line, spacer and gaskets along with the pump. I do not think you can source the parts much cheaper. You will not need the spring with the kit it should already be set for low pressure if it's for a VE pump.