efi with fuel pressure problems

[dirtdrdave]

While I like the idea of an adjustable one, I've never used one and the factory style has worked for many years and many millions of miles. So there's nothing wrong with continuing to utilize them.

There are still other things that can keep fuel from reaching the engine, but not many would keep fuel from the return line. Since it's just a big loop with only a few things in the middle, the list gets smaller. Never heard of a regulator stopping fuel completely, but I have to assume it's possible. I've had them apart, but can't remember even a small detail about them it was so long ago.
Not sure just how to test them either, but my thinking is that if your regulator was somehow able to block flow to through the lines, since it's at the far end of the engine side of things, you would still have fuel at the injectors. So why is that fuel not being injected?
Is there an in-situ test for injectors? Maybe your local parts store has a "noid light kit" you can rent/borrow to test the injector pulses. It's a light that you hook up to the injectors and it flashes each time the computer tells that injector to open and close. If you have a good pump and a good regulator and good plumbing, but the injectors are not firing, it would be good to know before buying a new pump and regulator.
And doesn't the TFI module tell the computer what's going on with the engine turning so that the computer can tell each injector when to fire?

I forget, what does the PIP test do? Isn't there an additional connector near the diagnostic port you can separate to put the computer into a different mode for checking the PIP signal?
Sorry I don't have the details in my head anymore. Just the vague notion that there are still other things that can help narrow it down.

Paul

Yes, you would think that even if there is no return, there should be fuel at the injectors to burn. I didn't know a noid light existed. I will try to find one. That seems like an importatn thing to evaluate.

 

[dirtdrdave]

You wrote that you got fuel flow at the rail with the pump running continuously but nothing through the return line. Did you try disconnecting the return line at the tank and then running the pump continuously? The regulator is just a spring and a diaphragm on a restricted orifice. The engine doesn't need to be running for it to flow gas, and as Dirtdonk noted there isn't much in that system to prevent return flow. Even if there was, pressure would then build in the fuel rail to the maximum pressure the pump could deliver and the engine should still run, albeit rich due to the high pressure.

Electric in-tank pumps generally either work or they don't. If your pump is flowing fuel I wouldn't be in a hurry to drop the tank. Makes me wonder if the injectors are opening.

Yes, I don't understand it. I know I have flow to the rails. I have no return out of the rails, but the pump keeps running and no pressure is recorded at the inlet to the fuel rails. You would think the pressure would just build and build. I don't understand what I am missing. If the pump is literally producing no pressure, would the fuel pressure regulator prevent return out the fuel rails to the tank in an effort to build pressure in the fuel rails?

How would checking for return of fuel at the tank give a different answer than checking return at the exit of the fuel rails? If there is no fuel coming out of the rails, wouldn't there also be no fuel returnig to the tank? I am not questioning you lars. I clearly don't know what I'm doing and I'm trying to understand! Thanks.

 

[lars]

Hmmm... Another thought, long shot.

Disconnect the supply line at the tank. Connect a fresh piece of tubing to the outlet and connect the other end to your pressure gauge. In other words, taking everything but the tank and pump out of the equation. Now run the pump and see what happens.

There is a line, or fitting, or something that connects the output of the pump to the supply nipple on the outside. If it's split or partially disconnected or whatever inside the tank, then the pump could supply fuel all the way to the engine when there is no restriction, but it won't build pressure. Instead it would bypass through the leak. The bad news would be that you'd have to drop the tank. The good news is it would probably be an easy (and inexpensive) fix.

 

[EPB72]

Yes, I don't understand it. I know I have flow to the rails. I have no return out of the rails, but the pump keeps running and no pressure is recorded at the inlet to the fuel rails. You would think the pressure would just build and build. I don't understand what I am missing. If the pump is literally producing no pressure, would the fuel pressure regulator prevent return out the fuel rails to the tank in an effort to build pressure in the fuel rails?

How would checking for return of fuel at the tank give a different answer than checking return at the exit of the fuel rails? If there is no fuel coming out of the rails, wouldn't there also be no fuel returnig to the tank? I am not questioning you lars. I clearly don't know what I'm doing and I'm trying to understand! Thanks.

In order for you to have return fuel the rail will need to reach the pressure spec of the regulator 30-40 psi ..it may have return flow at lower pressure but you say you have vey little and your pressure gauge reads near 0psi with every thing hooked up .... you can have good volume which you do [theres no head pressure /load being applied during test] your pressure is bad according to your gauge [two] at this point i'm starting to believe your gauge is correct and where you have it installed is fine,,,,,at this point i'd see if i can install the pressure gauge closer to the back near the tank install it just on the end of the hose/line no outlet and check your dead head pressure,,if not 80+ psi the problem is in the tank either pump or outlet hose between pump and sender assembly....

 

[EPB72]

Hmmm... Another thought, long shot.

Disconnect the supply line at the tank. Connect a fresh piece of tubing to the outlet and connect the other end to your pressure gauge. In other words, taking everything but the tank and pump out of the equation. Now run the pump and see what happens.

There is a line, or fitting, or something that connects the output of the pump to the supply nipple on the outside. If it's split or partially disconnected or whatever inside the tank, then the pump could supply fuel all the way to the engine when there is no restriction, but it won't build pressure. Instead it would bypass through the leak. The bad news would be that you'd have to drop the tank. The good news is it would probably be an easy (and inexpensive) fix.

YEAP.. Did'nt read this till after my post.....but not such a long shot ...seen this quite a few times,and sometimes it's the pump housing thats allowing the bypass,,,,

 

[Viperwolf1]

Stop messing around and drop the tank. The rubber supply hose from the pump has either split or slid off the nipple. I've seen it happen with the BC tank several times.

 

[dirtdrdave]

Hmmm... Another thought, long shot.

Disconnect the supply line at the tank. Connect a fresh piece of tubing to the outlet and connect the other end to your pressure gauge. In other words, taking everything but the tank and pump out of the equation. Now run the pump and see what happens.

There is a line, or fitting, or something that connects the output of the pump to the supply nipple on the outside. If it's split or partially disconnected or whatever inside the tank, then the pump could supply fuel all the way to the engine when there is no restriction, but it won't build pressure. Instead it would bypass through the leak. The bad news would be that you'd have to drop the tank. The good news is it would probably be an easy (and inexpensive) fix.

Thanks all. Update for today.
Got a noid light. The injectors are getting signals.
I replaced the pressure regulator (because that was easy). It didn't help.
Thanks for all the suggestions. I think I'll just drop the tank and see what I find.

 

[lars]

Stop messing around and drop the tank. The rubber supply hose from the pump has either split or slid off the nipple. I've seen it happen with the BC tank several times.

My external frame rail-mounted pump is LOUD. And the extra plumbing required for it and dual tanks is complex and UGLY. But every time I read something like that a certain serenity falls over me

Sounds like there is some room for improvement in that connection.

 

[DirtDonk]

...Including cutting a nice access hole in the tub floor!
Make a nice little panel to cover it up and seal the interior nicely, attach it with screws or whatever, and never have to drop the tank for pump maintenance/checking again.

paul

 

[lars]

...Including cutting a nice access hole in the tub floor!
Make a nice little panel to cover it up and seal the interior nicely, attach it with screws or whatever, and never have to drop the tank for pump maintenance/checking again.

paul

That's cheating <ducks for cover>

 

[DirtDonk]

Nah, I prefer to think of it as simply thinking ahead!
Working smarter, not harder sometimes takes more work...

Paul

 

[dirtdrdave]

So I removed the tank and pump. The biggest think that I found wrong was that the bracket holding the pump was not tight enough. The pump was still in the bracket, but had slipped down so the bottom of the pump with the filter sock was sitting on the bottom of the tank. I don't know if that would effect the pump's ability to pull in gas. Possibly.
The rubber hose, while kind of flimsy, was not torn or kinked.
There was a nut and washer on the bottom of the tank that I have not found a source for.
So, I guess I wil replace the pump, sock and hose and hope for the best!

 

[SC74]

Did you get it back together to see if it was the pump?

 

[dirtdrdave]

Did you get it back together to see if it was the pump?

Update:
I pulled the tank and as viperwolf1 and others thought, the hose in the fuel tank had a split in it. By that time, I had already ordered a new fuel pump, so I replaced everything inside the tank.

This tank/pump set up was from BC Broncos pre assembled. I had never previously taken it apart. What I believe happened was the fuel pump originally had a shim between the pump and the plastic bracket that holds it to the tank. This had disintegrated, I assume, because it was not there. The pump was therefore loose in the bracket and was hanging by the fuel hose. I think this weight hanging from the hose caused it's failure.

When I upgraded the pump, it was a larger diameter than the old pump so the bracket actually required some milling to fit around the pump. So there is currently no shim needed. So it should not slip over time. I also added a hose close around the pump above the bracket to prevent it from sliding in the bracket. This was suggested by BC Broncos.

It is currently running great!

Thanks everyone for all your help! This forum really is amazing!

 

[BUCKWILD]

The access panel in the floor is the best ever as DIRTDONK stated, I built mine when I built a tank and have had a pump fail on the trail. Pull the panel and remove the access in the tank and change pumps. Maby 30 min and back running. And I carry a spare piece of SAE 30R10 (submersible fuel line and not of the china manufactured type)hose and replaced it at the same time. I figure if the pump Fales time to change the hose.

 

[Boss Hugg]

Stop messing around and drop the tank. The rubber supply hose from the pump has either split or slid off the nipple. I've seen it happen with the BC tank several times.

\

It happened in my homemade tank when I was first trying to get the efi to crank. You talk about a nervous wreck. I had extended the harness to fit wheren I mounted the PCM... But I finally cut a hole in the bed where I could pull the FP without dropping the tank. Hose was kinked and hung on the end of the smooth "barb" where it attaches to the the pump. I put it back on, this time with a high pressure clamp, and I haven't had another problem.

After glancing thru this thread, I didn't see anything mentioned about a relay. If there is a relay involved, it could be bad and losing connection after it gets warmed up??

There absolutely SHOULD be fuel returning to the tank if the pump is running. It sounds like you have a pump problem and quite possible a stuck regulator.