Been having fuel problems with my '99 5.9 cummins. I've read several related and helpful threads on this forum and wanted to put my experience out there In anticipation of getting mine fixed and in hopes of helping someone else.

This truck was my dads and it had been parked for at the better part of 7 years. I had cranked it up to move around the yard a few times and remember that starting could be touchy unless you turned it on, let the LP run and then started.

I recently decided to put the truck back on the road and after a new set of tires, front end parts, fuel filter, batteries, etc., etc, attempted to make the first trip longer than 10 miles. At about mile 15, truck just died. I knew the LP was not running (making any noise) but my buddy said it ran out of fuel (was still showing 1/4 tank) so put 5 gallons in it with no luck. Cant remember if we bled at the injectors. Towed it home.

A few days later I went out to mess with it and the pump seemed to be coming on again. After bleeding at the injectors , got it started and drove 8 miles to the station and filled it up to 3/4 tank and convinced my self that it had just been out of fuel. Drove it around for a week on a few very short trips maybe 5 or 10 miles at a time with no obvious problems.

This week I drove it 12 miles to the store. I noticed the tach bobble a little and parked it real quick, went in got my stuff and came back out. Wouldnt start. Couldn't hear the LP running. Changed LP in the parking lot, got it running and drove back home. It seemed a little funny when I pulled in the drive. I parked, shut it off and tried to crank it right back. no luck. I read some posts on here about the LP power being supplied directly from the ECM.

Yesterday went out, hooked up an LED across the LP power leads and ran inside the cab so I could see exactly when voltage was being applied to the LP as I drove down the road. Bled it at the injectors cranked and went for a test drive. Made about 12-15 miles and the light (pump) was pretty much on steady but randomly would flash real quick several times in a row. It seemed like the light (LP) was on steady enough that the fuel pressure shouldn't be an issue. In the last mile back to the driveway, I showered down on it a few times. Turned into the driveway, coasting down the hill, and it dies.

I let it "cool off" and then tried to get it cranked for another hour until dark. Tried to bleed it all the way to the injectors, never could get fuel up there. Closed off the injectors and spun it several more times, eventually got where it would hit but not nearly enough to start it. The LED still indicates steady voltage of 12v to the pump during this time.


Went out to mess with it today. No change at first. It still hits a little bit, but never remotely enough to crank. Never can get fuel up to the injectors. I have bled fuel from all Banjo fitting right up to the IP. I'm staring to think my IP is bad. Decided I needed to be able to read the fuel pressure on the filter housing. Checked both brass plugs for fuel pressure with the LP running to see if one would be better than the other for a gauge port. When I opened the one nearest the driver side, there was as air pocket that took a full second of the LP running to purge. Once it purged I put the plug back in and the LP clearly sounded I like it was actually under load. I was able to get fuel to the Injectors, which I bleed, and cranked it up. The air pocket in that specific plug was surprising especially since I had bled all the banjo fittings right up to the IP and had fuel there.

Any way, my next move is to hook a fuel pressure gauge on the filter to see exactly what is going on. I have a suspicion that that pesky transistor in the ECM is putting 12v to the LP but not enough current which I think could explain low fuel pressure with a new LP. If that turns out to be the case, I'll hook a relay direct to the LP next

 

Today I went out hooked up a fuel pressure guage from the factory filter housing that I can see when I'm driving down the road. At idle I was showing 12-13 psi and at WOT had around 9. Headed out for a test drive and to make a long story short, the coasting and under load pressures started dropping gradually the further I went. By the time I was back at my driveway, I was barely on the throttle and struggling to be above 6.. All of a sudden the truck died as if out of fuel and I coasted in.

Tried to restart immediately and noticed LP was nor cycling after ignition on or key bump. I was encouraged and convinced i had found the problem. Erratic ECM power to the LP had to be it.

Wired up direct power to the LP harness and unplugged it from the ECM. Cranked up and had about the same pressures idling as before. Headed out on a test drive and basically did the same thing as before, slow but steady drop under load and coasting. The closer it got to 7, the more I eased up on the throttle trying to make it back.

After a total of about 12 or 15 miles, I headed up a hill near the house and as the pressure dropped below 5, it died again and the hardwired pump was showing 0 psi. I pulled it over and tried to restart. Was still showing 0.

Tried to bleed it at the brass plug on top of the filter housing. The fuel flow from the plug was choppy and eventually was just air. Though it might be out of fuel. Went and got 5 gallons but before I poured it in, decided to try and prime it again. It worked this time. Did not put the fuel in. I did have to crack an injector to get it started , but I was able to drive home. 12 psi idling and 9 under load for the 1/2 mile drive on home.

Now I'm thinking it's got to have trash or algae in the tank pickup, but that doesnt exactly fit the symptoms. Then I read another thread where the guy dropped his tank, cleaned everything and had the same or maybe even a little less pressure. Any way , I guess that will be my next logical move but I thought I'd just check for any other suggestions. Thanks!

 

The vent in the cap isn't plugged is it?

 

In the fuel cap? I have no idea. How would I know?

Thanks for the reply.

 

Leave the fuel fill cap really loose or off & take it for a drive.

 

First thing I did today was pour in the 5 gallons and headed out for a test drive with the fuel cap off. That didnt have any effect because I was having the same problems and eventually wound up on the side of the road. Realized I forgot my 19mm wrench to crack the injectors, luckily only about a 3 mile walk home today.

I never dropped the tank because the more I thought about it, the more I dont think its algae or trash. I probably will though, because its pulling a small amount of air from the tank or fuel line. When the truck shuts off, it always has be be bled first to the filter and then to the injectors. That air has to be coming from between the tank and LP.

At one point today I was beginning to think that maybe the IP was causing the pressure drop by letting too much fuel bypass and go straight back into the tank. This would not explain the air in the filter though. It is possible that this is happening but is not the only thing going on. I mean, I did have a problem with ECM power to the LP that has since been removed from the equation.

I do know that the LP is not super strong because the pressure varies +/- 1-2 psi from the acceleration depending on whether you are stopping or taking off. So if its possible for the fuel to bypass the IP and go straight back to the tank, it would definitely account for pressure dropping low enough to shut down. Anybody know if that's possible?

I guess my next move is to check the supply line to the lift pump and drop the tank if needed.

 

So, did you solve the issue?

 

No, I haven't solved it yet. I had a few other projects and things that needed to be taken care of. I plan to get back on the Dodge in the next few days. I will definitely update the thread with whatever happens next.

 

I was all in on your IP passing too much fuel back to the tank but then, like you said, there's the air in the line issue. Is the fuel heater in the filter housing sealed good? I had to rep[lace the O-ring in mine several years ago because it started leaking.
Also, some non OEM fuel pumps can cause issues if the pressure is too high. i had a higher pressure pump on mine and then had no hot start issue. Had to wait for the engine to cool down before it would start.