Rox Crusher's 77 sport

[Rox Crusher]

Tank back in, new gas added to cleaned tank, runs great again.

Well, that didn't last long (less than 50 miles actually)

[ZOSO]

You have more fuel pump issues than everyone here combined. Maybe a pink jeep is less problematic.......

Whats it doing now?

[Moab Mike]

You have more fuel pump issues than everyone here combined. Maybe a pink jeep is less problematic.......

Whats it doing now?

[Rox Crusher]

You have more fuel pump issues than everyone here combined. Maybe a pink jeep is less problematic.......

Whats it doing now?

It acts like it still has same fuel delivery issue. It stutters under medium to heavy load.

Since cleaning it and replacing pre-screen / strainer this last time, I put six gallons of strained fuel in it. It ran great. I filled up right before toys for tots. Ran like crap on way home. Man, I was (am) pissed.

The tank has two vertical walls in it which go from bottom to top and front to rear. The fuel moves between these sections by way of 4 or 5 large holes in each of these walls. So, it is impossible to see if there is crap in the other sections. All I can think is that there is stuff over there which gets to the pump when it is full enough for the stuff to be suspended in fuel and get through the lowest wall opening.

But as much as I cleaned the tank out I am beginning to think that I have another issue that I haven't considered since I thought the crap in the tank was the g gun.

[ZOSO]

I'd go through all sections. Disconnect the feed line at both the rails and pumps and blow air through the line backwards. check out the regulator too. pull and clean the injectors.


No new melted plug wires? If you get it running check temps on each header tube like we did in moab to find your bad wires. You may have an injector or two that is not working right.

Whats your fuel pressure? Maybe a bad regulator.

[airbur]

Where are your fuel filters Rox? Have you replaced them?

We have the exact same tank and pump. Mine hasn't had any issues.

[Rox Crusher]

Fuel filter is external to the tank, in very close proximity. It has been replaced.

Fuel pressure gauge usually reads 40 - 42. But I have also seen it at 30 on occasion, which speaks to the intermittent nature of the fuel delivery problem.

The first time I replaced the pump strainer it looked like the openings were clogged with small particles which I assumed were welding debris.

This last time, the crap in the tank wasn't necessarily clogging the openings in the strainer, but rather blocking them when they happen to get close enough to be sucked against it under hi-flow conditions. Only to be released under lighter flow. Well, that's my theory as to why it was happening intermittently and causing the inconsistent fuel gauge readings.

Zoso, there really isn't a way to get into the other two sections of the tank to insure they are clean. I guess I could get some sort of small plumber's camera in there or something.

Are you thinking the fuel pressure regulator could be bad and occasionally letting so much fuel return to the tank that it is causing the stumble ?

I guess checking the lines and injectors would be a good move, even as just a way to confirm they are working properly.

[ZOSO]

Yep. If the regulator gets "stuck open" it is letting too much fuel back to the tank and your not getting full pressure at the rails.

[Rox Crusher]

Yep. If the regulator gets "stuck open" it is letting too much fuel back to the tank and your not getting full pressure at the rails.

Do they stick open intermittently ?

[ZOSO]

im not sure but it's always possible. Even tho they are non adjustable there is always a possibility that the regulator is failing.

[airbur]

Hers how to fix it....

[ZOSO]

Yep ^^^^^

[Rox Crusher]

Well, I'm just hoping that it is something other than crap in the tank again.

I can't believe there would be enough probability of the strainer becoming clogged / blocked again in under 70 miles.

[ZOSO]

I'd start everywhere but the tank. I'd start by changing the filter. it's the cheapest part.

[Rox Crusher]

Changed fuel filter, went for 30 mile test drive, problem still persists.

Fuel pressure at warm idle is inconsistant. The other day it was 40, earlier today it was 34, at parts store it was 30, just now it was back at 34.

Gonna let it cool down and change the fuel pressure regulator.

[Rox Crusher]

Note to self: always allow fuel pressure to bleed completely off such that guage reads 0 instead of being impatient and doing it when it still reads 5 psi.

Installed new FPR, gauge reads 36 at warm idle, and will increase to 42 with throttle. The other FPR didn't reflect any change in PSI with throttle.

Unfortunately, this didn't solve it either.

I guess next step is injectors ?

Any other ideas ?

[ZOSO]

Does this do it just idling or do you have to be driving?

[Rox Crusher]

Does this do it just idling or do you have to be driving?

Can't get it to do it in the driveway.

Does it while driving.

Most noticeable when in 3rd gear at 2,500 to 3000 rpm. The farther you go, the worse it gets.

Can make it go away by stomping on gas and increasing RPM / and or downshift.

[ZOSO]

need to remote mount the fuel pressure gauge and possibly get a wideband o2 in there to see what it's doing. What are the actual symptoms? If it's just in that short window in only that gear under that particular load it makes me think it's more electrical. Do you have an oiled air filter on it? Have you pulled the MAF and cleaned the wire?

[Rox Crusher]

need to remote mount the fuel pressure gauge and possibly get a wideband o2 in there to see what it's doing. What are the actual symptoms? If it's just in that short window in only that gear under that particular load it makes me think it's more electrical. Do you have an oiled air filter on it? Have you pulled the MAF and cleaned the wire?

It isn't just in that band, just far more pronounced.

Dry filter that needs cleaned again.

I will clean MAF wire.

Remote mount as in a long ass hose so you can see it in cab while driving ?

[Rox Crusher]

Symptoms best described as a continuos short choppy stutter / stammer.

[ZOSO]

Yes just dont put it in the cab. Like tape it to the fender or something. Another thing is to hook up with Airbur or EFIguy and see if they can data log it. I dont have the software to do the older EFI systems. It is fuel related if it goes away when you mash on it. Another thing to check it voltage. What gauge wire do you have running to the pump? Is it ok when cold and get worse after driving for a while?

Have you thrown a timing light on it lately?

[ZOSO]

another thing is have you pulled the plugs? I wonder if something happened and on is out of gap.

[Rox Crusher]

another thing is have you pulled the plugs? I wonder if something happened and on is out of gap.

I thought of that last night too.

I have my shorty plugs laying around so I will put them in today.

Do you happen to know the proper gap ? The guy at orielly's told .054 which sounds excessive.

[Rox Crusher]

Another thing to check it voltage. What gauge wire do you have running to the pump?

Is it ok when cold and get worse after driving for a while?

Have you thrown a timing light on it lately?

Dont know what the wire gauge is, whatever came with the EFI harness and the connector harness for the pump. I did solder a piece in but it is same size.

Haven't really paid enough attention if it is different when cold vs hot.

[Viperwolf1]

Do you happen to know the proper gap ? The guy at orielly's told .054 which sounds excessive.

That sounds right.

[Moab Mike]

.054" gap and torque to 7 to 14 ft lbs. per the Haynes manual.

[ZOSO]

The fuel pressure may be fluctuating cause the engine vacuum is doing the same. Either you have a vacuum leak or a timing issue. those are cheap things to look into also.

[B.O.B.]

mine is doing the exact same thing. Been trying to solve this issue for 6 months and still can't get it figured out.

[landshark]

i was going to mention vacuum leak as well... maybe upper intake gasket leak? TB gasket? etc?