justagoodolboy

I have a FP gauge on my truck, and it bounces between 11 & 16 PSI at any point during a run through the gears with or without a heavy foot. It twitches a little at idle. When its doing this, it is totally gutless when it comes to power. I originally thought I was sucking air somewhere, but after a new pickup in the tank and 3/8 line plus 2 new piston LP's, I ruled out any air. However, what was strange, was when I would run the truck on a 5 gallon diesel jug in the bed through clear hose by the window it would run really strong with no air in the lines and no bouncing FP gauge, then after about 10 miles start the bouncing again and lose power, and once I hooked up the fuel supply from the tank it would do the same, run stout for a while with the FP gauge barely coming off 16 PSI, then the gauge would start bouncing when accelerating and it would lose power.

When it ate the first solenoid, it took a big chuck out of it, so I ground down the solenoid per the sticky, and fixed it. When I took the solenoid out, the FP gauge was doing its normal bouncing, and when I put it back "fixed" it continued with the same low power.

The second time around was different when it ate the fixed solenoid. It took an even larger chunk out of it, and I took it completely out and starting killing my truck manually awaiting my new solenoid to come in. During this time I noticed with no solenoid the FP gauge did not bounce, and it would break the tires loose into 3rd like it used too and was a VERY noticeable increase of power and fuel economy.

But, that did not last long, after about 4 days of driving it, it started the bouncing again, and loss power. My new solenoid came in, so I installed it, and the power was back and the FP gauge was steady for a few days. Then it ate the new solenoid, and the loss of power back and bouncing gauge. So i removed it again, this time for good, and went to the pull cable. Just as before the power and steady FP reading came back for a few days, and now its back to loss of power.

However, I have noticed that when it sits, the FP gets steady, and the power is there, but you run it for a few miles, and its back to bouncing pressure and no power.

All I can think is these chunks of rubber from the solenoid are stopping something up, and when it sets they settle out of the way allowing for full fuel. I've checked the return line screen, and it was stopped up pretty good, but did not help cleaning it, and I even flushed the pump via the manual pump on the LP when I had the solenoid out, still to no avail.

I just feel like I am close to resolution, but don't want to pay for a "rebuild" on the pump to clean out some junk that will obviously return my truck to normal. Much appreciated to anyone who read my "book" to this point - THANK YOU.

-Jeff

KD93

I don't mean to offend, but you've checked your fuel filter right? Double gasketed maybe? I know it sounds dumb, but the age-old addage is to start with the simplist things first. Also, I know you said you've changed your pickup tube in the fuel tank, but did you check the quality of the fuel or if there's anything floating around in the tank that could block the pickup off? 'Cause after driving around for a few miles you're going to mix up all the nasties in the tank.

.... No, that probably isn't so 'cause you had the 5 gallon jug feeding the fuel for a trip. Mmm. maybe you're right and there's foreign debris still in the pump.

justagoodolboy

No Sir, your not going to offend me, I appreciate your response! When this all started, I changed the filter right off, and since changed it several times since, as this problem has been going on for around a year or so (my truck's not a daily driver).

The reason for my initial inspection of the tank was thinking either there was junk in the bottom of the tank stopping the screen up on the bottom of the pickup assemble, and to clean it out. However, I found a super clean tank. Since I was still thinking I might be sucking air, I just put a new pickup straw on it for good measure.

I'm leaning to the possibility of debris in the pump, but I have no clue where to look, and to be honest don't feel confident in my ability to tear into the VE. However, I don't want to go spend a bunch of $ at the pump shop on a simple fix either....

Partsdude

Since you are looking to try the cheap route first as would I, have you checked the seal washers on the banjo bolts? The VE does have some suction to it and it may be pulling air from them seals. I'd put a clean rag or bucket under the pump just in case anything like crud from the tank or a failed seal fell out.
Have you noticed if your power problem is heat related? (low power when the engine is warmed up vs. when it is cold?)

justagoodolboy

I have not checked those seals. That might not be a bad idea. Best I can tell its not heat related, but my heat gauge does act differently if you can believe that - when its getting good FP without the bounce, it'll run up and get hot like it used to on a WOT run, but when its bouncing, it stays in the center of the gauge or less regardless of what you do.

With that said, if the FP gauge starts bouncing, you can let the truck sit for 5 minutes or so idling, it'll level back out and have more power for a shorter period than when you first start it for the day, then back to bouncing.

It also does it with a full tank, so its not the draw straw sucking air, plus it was doing it with the factory pickup assembly.

Alec

Are you SURE that the return and suction lines to the tank are not leaking or plugged? That is really what it sounds like to me, either an air leak or more likely, a clog in a fuel line. It doesn't sound like a problem inside the injector pump that I can think of.

wannadiesel

^I'm with him. You have a supply issue somewhere.

KD93

Not sure if you've tried this, but unplug your supply line from the LP and blow in to it. Or use your compressor, but that's sometimes a little loud. Get someone, or yourself if you can bend the line that far, to listen at the tank for the bubbles that you should be able to hear. It's not completely foolproof, 'cause air can move around any foreign debris, but it may help eliminate that particular piece of the puzzle.

justagoodolboy

The only line I did not address was the return line. When it started doing it with the factory supply line, I then upgraded to a 3/8" line and put a new pickup in the tank and everything. That line from the LP to the pickup tube would hold pressure and vaccum, so I just cannot see it being anything from the LP back.

However, I have never touched the hard lines from the LP to the VE other than changing to the tapped banjo for the FP gauge and installing the new hard line for the Piston LP.

More questions if it is indeed supply:

- Could the return line be causing this? I did check the return banjo at the VE and it had a decent amount of crud in it.

- If I don't have visible leaks from the LP to the VE on the hard lines, then in theory they could be ruled out from sucking air unless blocked internally.

- Is there a sort of vaccum vs. pressure equilibrium of sorts in the tank that the return line offsets, and my boucning FP gauge and subsequent loss of power be from the LP pulling a vaccum on the tank and this not being able to supply the VE with fuel. That said though, it still does it even with my fuel cap loose.

wannadiesel

Man, I am stumped then.

I don't know that the bouncing gauge really has anything to do with it. When I'm running on the piston pump, my gauge bounces but it does not affect power.

What it really sounds like is that when the pump gets hot, the engine loses power. That makes me think "tired VE."

Bob Beauchaine

Since the VE is cooled by fuel the opposite could be true - that is lack of fuel is letting the IP get hot. Are you by any chance running Bio Diesel or a strong mix if Bio/#2?

Bob

Boatnik

When my shutdown solinoid failed the first time, I found rubber in the return line banjo bolt orifices. It only created a leak on the VE case. Thinking of that, could you have switched the banjo bolts around on the VE? The return has a very small hole in it compared to the supply which usually needs drilling a little bigger.

justagoodolboy

No bio or any mix thereof. Just straight ULSD with the recommended dash of power service.

I agree - the gauge is the oddity. I wish someone was close enough to take a ride, its really stange as bouncing needle means low power, steady needle means hold on. I was thinking the same thing on the VE getting hot, but if the truck sits and idles for 5 minutes or so sometimes (not every time) you can jump back in it and have the stead fuel pressue and the power is there.


No way I could have swapped them - I did not even know of the screen in the return banjo until a few weeks ago when I checked it.


I'm stumped too!

Partsdude

I say you have a failed / failing lift pump by this description. At an idle - the LP can supply enough fuel to cool and power the truck. Once you drive it a bit, the VE uses up the supply that the weak LP had causing the gauge to jump. Let it idle and the LP manages to resupply enough fuel for it to run good for a bit.

justagoodolboy

I thought so too, but I've tried 2 new Piston LP's and they do the same thing, so I don't think its the LP. What's sad is I've resorted to just throwing parts at my truck out of frustration, all the while that being what aggravates me so much about people that call themselves "mechanics" yet cannot fix anything.....