Long story short...Truck stumbles and now fuel pressure falls to 0 with an Essex pump, a Holley blue or a stock pump when rpms are above 2000 in neutral. On the road, truck dies under load.

I had a MAPS code and had a TSB ECM reflash initially. Yesterday fuel pressure was 15 at idle with the Essex pump, 10-12 under load and WOT...but I had a stumble at 70 MPH with a chatter in the top end of the engine. Feather the throttle and the chatter would go away.

Another thing to note is when the truck would stumble, the fuel pressure on the highway would go from 10-12 back to 15 and I had no throttle...but it did not slow down either. Flooring it made no difference...boost and egt stayed the same.

Changed out the fuel filter before I went to Denver, in Denver and when I got back. Changed it again today. Back to the stumble...after about 10-15 seconds the engine would stumble again, the fuel pressure would go back to 10-12 and the power would be back.

We tested the pop off and it was fine. Replaced it anyway...no change.

After all of this the service mgr., tech and DC are thinking we should vacuum test the fuel line from the tank at the lift pump and see if we get a restriction. I kind of agree with this but wouldn't the fuel pressure go up instead of down if it was sucking harder?

All my injection lines at the head were way off the torque spec so we fixed those and no change. We did the fuel flow test on the Essex as per Dodge...removed the fuel line at the CP3, turn key on, count to ten and measure amount of fuel. If its 380 Milliliters, its fine.
We got 420 with the Essex, 380 with the stock pump and 390 with the holley.

Anyone have any ideas?

Its an 04 6 spd currently running stock power. We even tried it out with the Ramifier on at different levels, no change in anything.

Scotty

 

A restriction between the pump and somewhere inside the tank could cause that. I think the vacuum test is a good idea. A restriction would explain the relative low flow rates. I would think that a free flowing line should yield a lot more fuel then your numbers.
Could you have a partially clogged strainer in the tank?

 

That is what we are checking tomorrow. We have checked everything starting at the front and working backwards. We even thought about the fuel pressure gauge but ruled it out with another one and the fact that all three pumps where losing pressure.

I suggested the pick up tube in the tank but we will know soon enough.

The Essex is a 160 gph pump...I agree it should have pumped a lot more fuel.
We are going to check the voltage and amperage to the pump [s] tomorrow as well.
They had one truck that had a similar problem and it was the ECM sending messed up signals and no codes.

Scotty

 

Have you ever dropped your tank and checked the pickup tube screen for debris or the tank itself for crud? Just a thought, no mechanic here just a can't leave well enough alone kind of guy. I just like to rule out all thing mechanical and hate to deal with anything software.

 

I also believe crud has plugged up the pickup screen in the fuel tank.

MikeyB

 

The vacuum test on the supply line is what is leading us to dropping the tank.
I agree with this as being the problem. This would also explain the shudder/stutter at 70 mph if it was just starting to clog. It also makes sense that its gradually getting worse and the last time I stopped it, something else must have covered the screen to cause the pressure loss. I hope to know more in the next hour.

Scotty

 

Well, they tried a different ECM, no start and put the old one back in. Voltage fine to the pump. I now have the in tank lift pump.
Then they changed the fuel filter...which had been changed 3 times since June 25. I changed it before we went to Denver, changed it again in Denver and changed it again on the way back. Dealer thought they had the problem solved and it did appear that way but with much lower fuel pressure. I take the truck for a ride in the city and pull the fuel pressure from 7 at idle to 3 and then 0. I am not even going out on the highway like this.

we cut the filter open and it was clean clear through.

Scotty

p.s. the screen was clean in the tank, tank was clean...very clean. Nothing plugged.

We unhooked the Holley Blue and tried the fuel flow test and it only poured out 110 ML now.

Checked voltage, all is good.

I am going to put fuel in from a different place tomorrow and see if I got some crap fuel. I am grasping at straws. I still think its injectors and/or the CP3.

 

Somethings not right. If the holley first pumped out 390ml and now it's only pumping 110ml, something has to be clogged. Did you retry the other pumps after you did the holley? Are you trying the flow test directly out of the holley or somewhere else? If it turns out to be the injectors then this would be the perfect time for a set of Flux injectors. Why didn't the new ECM start the truck?

 

sorta sounds like the cp3 is going south

 

The fuel flow test is done by removing the fuel line that supplies the CP3, and you turn on the ignition and let the lift pump run for 10 seconds and measure the fuel collected.

So we did determine the fuel supply is being hit prior to the CP3.

This also lead us to try another ECM. I found out the ECM was off an 03, thats why it did not run. Then we thought it could be the voltage or an amperage draw making the pumps run weak...that all checked out.

I am going to blow compressed air back into the tank on the supply line at the filter housing tomorrow as suggested by another member on here and see if I got something in that supply line. The in tank pump is about half of what it should be for stock and the dealer is not sure what to do now.

I fully expected to have good fuel pressure with the intank pump and was prepared to pay the bill and blame the Essex pump...I should have bet them something.

We also changed out the pop off valve again and left the new one in.

Scotty

 

Fuel pressure would go DOWN if it was sucking harder. When I was having my fuel tank pressurization issue, FP was much higher-- up to 20. Once the tank pressurization was gone (i.e., the pump never had to suck), FP came back down to 15-17.

Your service mgr and DC are correct in looking for a restriction in the pump feedlines.

HTH

Justin

 

They claim they checked that and got no indication of a restriction. This is why I want to do this in reverse. Its got to be something simple and obvious. We know the flow is lower on all of the pumps then normal right after the fuel filter to the injector pump but its on its 4th fuel filter now and a supposed cure all from DC with the new in tank tsb pump installed.

Next thing I might do is add an inline pump of my own with a filter between the in tank pump and the one I will add. I will also put a regulator on the second pump and yes I will have it plumbed to be bypassed. What kind of relay would I need to run a second pump and how should it be hooked up? I noticed that the in tank pump taps into existing wiring and has a relay on it. I wonder if I can make the 2nd pump work the same way with a different supply of power? Thinking out loud can be scarey.

LOL

Scotty

 

Quick thought from a dummy if I may......

Were the fuel passages between the fuel cannister to the injector pump ever blown out?

Or was it just from the cannister back to the tank?

 

I have my own fuel line kit from the filter housing to the injector pump and just for the sake of being careful, I put new hose on there when we were testing the flow of the pumps. No difference.

However, something else has crossed my mind...

I am thinking I may have a cracked filter housing cap. If its pulling in some air, that would cause a loss of pressure from the pump [s] and I may have cracked it last time I replaced a filter...and since that canister has been opened several times in the last month...it may even be cross threaded. Since the dealer says everything is good in front of the filter housing...Maybe that is the problem...I will pull it off of there when I know for sure on Monday that they have a replacement.

Scotty

 

is the filter after the pump or before? if the filter housing was cracked/crossthreaded, you would have a fuel leak unless you were pulling a vacuum. positive press would leak diesel. could the tank vent be blocked and not letting air into the tank?