Need a little help

[DarkMonohue]

Disregard. Mistakes were made.

[DarkMonohue]

Hold on, I'm confusing myself here. I have a lot on my mind and am trying rather unsuccessfully to multitask. Feel free to disregard anything I have said. Same as usual, really.

[DarkMonohue]

Alright. I messed up. Not sure what I have been smoking. The regulator is downstream from the injectors. Whatever pressure you see on the external gauge is the pressure at the injectors.

We can still block off the return hose as a test to see whether the low pressure is the result of a faulty regulator sticking open or a result of the pump not moving enough fuel.

Sorry, guys. I don't know how I got so wrong, but definitely made things worse here. I guess I have a lot on my mind lately.

[Crankyolman]

I don't think you made anything worse Darkmoon. I basically knew that the system will show whatever pressure it is at no matter where you place the gauge upstream of the regulator.



My current thoughts are

1) Get an AN6 cap to block off the return line and see what happens. The system is capable of running as a returnless system but I understand this is bad for the pump but it's a way to determine what the output pressure of the pump is.


2) run pump directly off the battery and see what happens.


3) place my little spy cam under the hood and record what the fuel pressure is doing while driving and see what's happening.

[DarkMonohue]

These are all excellent ideas.

I wonder whether you could wire the pump through a switch so that you can select between powering it through the ECU to powering it directly off the battery. That would allow you to switch to battery power when it starts to run poorly and see if it returns to normal running behavior.

And I still have my doubts about the ability of the ECU to provide adequate current under load. Reading voltage at the pump would be nice as well.

You're getting close. This will get fixed one way or another!

[Crankyolman]

I've been messing with the truck and here is where I am.I rewired the fuel pump so it is operated by a relay rather than through the ECU. Starting fuel pressure was 46psi, dropped to 37psi after start and seemed to run better so I took it for a drive. A couple miles down the road on acceleration fuel pressure dropped to 30, AFR spiked to 20 and when accelerated fuel pressure continued to drop until it died. immediately after it died and before turning the key off fuel pressure went back up to 42psi. After letting it it sit about 2 minutes, it started fine and ran fine for about a mile then pressure began dropping again and same problem.



I decided to try a frame mounted pump and never even took it for a drive. The frame mounted pump made no difference and was unbearably loud even though it was well below the tank and carefully primed.



So, any ideas? I thought maybe capping the return line and seeing what that does but Fitech said not to do that.



Could it be both the in tank and the new frame mounted pump are bad? Anybody have a suggestion for a better in tank pump that can produce 50-58psi?



Maybe some kind of blockage, I don't know where that might be. There is a strainer bag on the pump in the tank that should prevent anything in the tank from doing that.



I have a flex line going from the tank to a hard line, which goes most of the way and a short length of flex line to the throttle body, then a flex line returning fuel back to the tank.



I'm seriously at a loss here. Could it be the regulator in the throttle body is failing? Maybe I need to ignore the Fitech guy and cap the return line and drive it and see. I just don't know what to do next.

[rang-a-stang]

You're in the ball park, Cranky! Don't get too discouraged! You can be fairly certain that your problems are fuel pressure. That's a lot farther down troubleshooting tree than when you started.

So new question is: Why is my (your) fuel pressure dropping?
So either your pump is not moving the volume of fuel it needs to in order to maintain the pressure you need or your regulator is dying. I do not think it is your regulator because when demand is low (at idle) your pressure is good. I think volume is your problem.

You mentioned the strainer. How clean was your tank before the install? Was your tank completely sealed up while you were sanding body parts? If your tank was dirty or not sealed up, your sock could be clogged. In my mind, this seems like the most likely cause.

When you had both pumps in series, did you energize them both? If you did not, then the inline pump was trying to pull fuel through the in tank pump so that may be why it didn't seem to work. It may also be why it is so loud. My inline pump is almost completely silent. I really have to get under my truck to hear the pump itself. I can usually hear the fuel swoosh through my throttle body more than the pump when I energize my pump and the engine is not running.

I also read a story a long time ago (on this forum) about someone who's fuel pickup was too close to the bottom of the tank and when fuel demand went up, it would suck itself to the bottom of the tank, pressure would drop, truck would stall, suction dropped, pickup would separate from the tank bottom, truck would start back up, and the cycle would repeat. I think this is very unlikely in your case but the symptoms were very similar to yours.

Last thought, I wonder if those flex lines you mentioned were not alcohol safe, the fuel that sat in them had alcohol in it, and maybe with fuel sitting in them, they have gotten soft as they sat. Then, when demand goes up, the fuel line collapses. This is probably not likely but maybe.

You're close Cranky! You got this!

[babywag]

quick test...
unplug/cap vacuum hose to regulator.
with no vacuum signal it should maintain it's set pressure 43.5 or 58

fire up and idle for quick check and if pressure ok take it for a short drive
if pressure dives again pump weak or possibly restriction somewhere?

[Crankyolman]

It seems we are coming to the point where I am going to have to drop the tank and at the very least pull the pump out to try to use the in line pump. I'm not very thrilled with that idea but it seems this is where we are. I just need to find enough containers for the 19-20 gallons of gas that is in it. One problem I'm having is that if I'm pulling the in tank pump I would prefer to replace it with another in tank pump but the in line is what I have so hopefully it behaves better after removing the in tank pump.

You're in the ball park, Cranky! Don't get too discouraged! You can be fairly certain that your problems are fuel pressure. That's a lot farther down troubleshooting tree than when you started.

I'm trying not to be discouraged but it's not easy and Mrs. Cranky is very unhappy with the situation of the truck being down and her not being able to roam the world at will when I'm at work.

So new question is: Why is my (your) fuel pressure dropping?
So either your pump is not moving the volume of fuel it needs to in order to maintain the pressure you need or your regulator is dying. I do not think it is your regulator because when demand is low (at idle) your pressure is good. I think volume is your problem.

I'm thinking the same thing, I was thinking about the possibility that it is a collapsing line and thinking about replacing the inlet flex line with one of the lines I made up to extend the system when I moved the truck out of the garage but really don't think that is the issue and I'm pretty sure those lines have 45* fittings and not 37* so it would only be a temporary thing for testing.

You mentioned the strainer. How clean was your tank before the install? Was your tank completely sealed up while you were sanding body parts? If your tank was dirty or not sealed up, your sock could be clogged. In my mind, this seems like the most likely cause.

The tank has always been quite clean. It's a newer poly tank. It was fully closed while sanding and painting. it actually wasn't disconnected from the wooden framework that supported the granny flat bed until after painting and was dropped and open for a minimal amount of time.

When you had both pumps in series, did you energize them both? If you did not, then the inline pump was trying to pull fuel through the in tank pump so that may be why it didn't seem to work. It may also be why it is so loud. My inline pump is almost completely silent. I really have to get under my truck to hear the pump itself. I can usually hear the fuel swoosh through my throttle body more than the pump when I energize my pump and the engine is not running.

Yes, I ran the in tank pump directly off the battery and verified pressure prior to running the in line pump off the ECU.

I also read a story a long time ago (on this forum) about someone who's fuel pickup was too close to the bottom of the tank and when fuel demand went up, it would suck itself to the bottom of the tank, pressure would drop, truck would stall, suction dropped, pickup would separate from the tank bottom, truck would start back up, and the cycle would repeat. I think this is very unlikely in your case but the symptoms were very similar to yours.

I don't think that is the case since it has been fine for an entire year.

You're close Cranky! You got this!

I hope your right because I'm awfully close to putting that old crappy carb back on.

quick test...
unplug/cap vacuum hose to regulator.
with no vacuum signal it should maintain it's set pressure 43.5 or 58

fire up and idle for quick check and if pressure ok take it for a short drive
if pressure dives again pump weak or possibly restriction somewhere?

I will see if I can do that before I start draining the tank to remove the in tank pump.

[DarkMonohue]

How about that regulator? FiTech says it's an OEM style unit. What is the OEM application? How hard is it to reach and how much is a parts store replacement? If it's cheap enough to try and easy enough to replace, it may be worth a try.

[Crankyolman]

How about that regulator? FiTech says it's an OEM style unit. What is the OEM application? How hard is it to reach and how much is a parts store replacement? If it's cheap enough to try and easy enough to replace, it may be worth a try.

I think it's the round silver thing on the front of the throttle body, which should make access super easy but I have no idea what part they used for it.

[DarkMonohue]

I think it's the round silver thing on the front of the throttle body, which should make access super easy but I have no idea what part they used for it.

I bet you are right. I wonder if it's GM TBI, since what you have is similar to TBI in overall layout.

[babywag]

Definitely no GM TBI parts used on your system.
Quick Google search comes up with this...

https://www.rockauto.com/en/parts/bosch,0280160557,fuel+injection+pressure+regulator,6124

I would verify with fitech. Their website states your system is 43.5psi

[DarkMonohue]

Definitely no GM TBI parts used on your system.
Quick Google search comes up with this...

https://www.rockauto.com/en/parts/bosch,0280160557,fuel+injection+pressure+regulator,6124

I would verify with fitech. Their website states your system is 43.5psi

Your internet skills are better than mine. I made the mistake of going to FiTech for information. Not exactly fruitful.

If that's the style, and there's an external vacuum line, you have a few ways to test it out. I think a fix is right around the corner.

[Crankyolman]

OK I've been doing some more research and it seems they use 2 different pressure regulators depending on the system. Back when I first got it their website had little to no info on what parts it used or even the pressure. Somewhere, maybe from my first contacting them I was informed that it was a 58psi system but now they say 43.5. if it is a 43.5psi system it uses a Bosch 3 bar 0280160557 regulator and the 58psi system uses a Bosch 4 bar 0280160575, they are both about $25, which isn't too bad. I've seen people say they have swapped out the 43.5 for the 58 but don't really understand why or the benefits. Fitech seem to use a lot of 0-year Volkswagen parts, at least the o2 sensor and the fuel pressure regulator seem to be.



This morning I did what Babywag suggested and disconnected the vacuum line to the pressure regulator. I've found some posts where the regulator caused this exact problem and found out that you can disconnect the vacuum with no issues and that Fitech has told people it isn't really needed. So I disconnected it, turned on the key and fuel pressure read 48psi. I started it up and fuel pressure continued to read 48psi. I revved it a little and there was no drop in pressure so I took it for a drive. It went a little further this time but just before I got home I saw the AFR start to increase and sure enough when I got in the driveway and revved it pressure dropped off sharply.



So I set to work draining the tank by first disconnecting the fuel line, then aiming it into the gas can. It only trickled out, so BINGO we found the problem! I left that running and it took about 30 to 45 minutes to fill the 5 gallon can That got it low enough for me to pull the filler hose off and get a siphon hose in there and drain the rest.


I dropped the tank, pulled the fuel pump and it had more debris in it than I think it should and possibly that was enough to cause the problem but I took the pump out of the system anyway. It's all back together now except for the pump, I will install that tomorrow after I fab a coupling so I can mount it just aft of where I have the down stream filter mounted. Hopefully it will not be as loud anymore. I think I will test the old in tank pump and see if it looks like it will work after cleaning out the debris and if it does I will hang onto it in case I ever have to do an emergency thing on the side of the road but maybe I'll just buy a spare frame mounted pump when I eventually save up enough amazon gift cards from Bing