This is on a Formula pushrod 3.4. The engine swap was done years ago, and ran perfectly for years. The car sat for about 8 years, and I'm trying to revive it. I replaced the fuel pump, cleaned the injectors, new battery. Did the factory manual tests on the evaporative canister. Starts, runs and idles fine. After revving the engine, and/or driving it up and down the block, the fuel pressure drops from 34 lbs to less than 20 lbs, and if you keep advancing the throttle it drops more and will stall. I suspect a bad new fuel pump, or some kind of vapor lock. I really need some suggestions. Thanks.
Check to make sure your tank is not creating a vacuum, that the pump is having to work against. The easiest way is to loosen the gas cap, and see if the problem is still there. If it goes away, start troubleshooting the vent lines from the tank. Try unplugging and capping the vacuum line to the FPR. With no vacuum, it should show increased pressure. Or at least no major reduction. Also try blocking off the return line. (I've seen some "dull" plastic pliers that are used for just that purpose. Clamps the rubber line without pinching or cutting anything.)
[This message has been edited by Raydar (edited 06-26-2020).]
Regarding the fuel pressure regulator test, unplug the vacuum line from the FPR while the engine is idling. That will trick the FPR into thinking the engine is at wide-open throttle. Fuel pressure should increase by about 8-10 PSI. If it doesn't, the FPR is probably faulty.
Check to make sure your tank is not creating a vacuum, that the pump is having to work against. The easiest way is to loosen the gas cap, and see if the problem is still there. If it goes away, start troubleshooting the vent lines from the tank. Try unplugging and capping the vacuum line to the FPR. With no vacuum, it should show increased pressure. Or at least no major reduction. Also try blocking off the return line. (I've seen some "dull" plastic pliers that are used for just that purpose. Clamps the rubber line without pinching or cutting anything.)
I ran some of these tests. I loosened the fuel cap, and there wasn't a change. But the car is on the lift, so it isn't under load. It had fluctuations in fuel pressure, but I wasn't able to replicate the problem of the pressure dropping way off.
Before I take the car off the lift and run it under load, I wanted to talk about the Fuel Vapor Tank, which is located under and forward of the battery. Is there any possible issue that can cause problems with this tank?
Regarding the fuel pressure regulator test, unplug the vacuum line from the FPR while the engine is idling. That will trick the FPR into thinking the engine is at wide-open throttle. Fuel pressure should increase by about 8-10 PSI. If it doesn't, the FPR is probably faulty.
I was able to pop the vacuum line off while running, but there wasn't room to cap off the vacuum line. The pressure did go up, but I'm wondering if that could happen due to now having a vacuum leak?
Started the car, got it warm and run up up and down the block. Same problem, fuel pressure drops way down, drops more the more throttle you give. During the warm up, revving the engine, it was sputtering and backfiring. When running under power, it pings.
Optimally, fuel pressure should be above 40 psi at idle. The stock regulator is set at 43.5 psi and that's what it should provide when the fuel rail is primed without the engine running. After the engine starts, ideally, the pressure shouldn't drop below 38 psi. With it sitting as long as it has, there's probably a bunch of sediment in the tank. We lost a set of injectors after a car had set for about 4 years, and even a fresh fuel filter didn't prevent the superfine particles from passing through and clogging the inlet to some of the injectors.
[This message has been edited by fierofool (edited 06-26-2020).]
Did you put in a new rubber line that goes from the the pump to the line that runs to the injector rail hardline? they look good untill pressure builds up and then they leak and bleed off pressure.
------------------ 86 GT built 2.2 ecotec turbo rear SLA suspension QA1 coilovers on tube arms
Optimally, fuel pressure should be above 40 psi at idle. The stock regulator is set at 43.5 psi and that's what it should provide when the fuel rail is primed without the engine running. After the engine starts, ideally, the pressure shouldn't drop below 38 psi. With it sitting as long as it has, there's probably a bunch of sediment in the tank. We lost a set of injectors after a car had set for about 4 years, and even a fresh fuel filter didn't prevent the superfine particles from passing through and clogging the inlet to some of the injectors.
I drained all the old fuel when i changed the pump, and made sure the tank was clean.
Did you put in a new rubber line that goes from the the pump to the line that runs to the injector rail hardline? they look good untill pressure builds up and then they leak and bleed off pressure.
I replaced all of the rubber lines on the back of the tank with new parts, including the two curved hoses that go to the gas fill.
I replaced all of the rubber lines on the back of the tank with new parts, including the two curved hoses that go to the gas fill.
I'm not sure you actually answered the question, as I believe wftb was referring to the short piece of submersible hose in the tank.
quote
Originally posted by wftb:
Did you put in a new rubber line that goes from the pump to the line that runs to the injector rail hardline? they look good untill pressure builds up and then they leak and bleed off pressure.
I drained all the old fuel when i changed the pump, and made sure the tank was clean.
We did, too. Even took a water hose and washed the tank out. It was horrible inside. The water coming out after rinsing was nice and clean.
Installed a new pump and screen and removed the pulsator due to bad seals in it. Not only did we have to replace the injectors, but the new Bosch pump failed, too. MikeMac then rinsed it with a commercial wash.
I'm not sure you actually answered the question, as I believe wftb was referring to the short piece of submersible hose in the tank.
[QUOTE]Originally posted by wftb:
Did you put in a new rubber line that goes from the pump to the line that runs to the injector rail hardline? they look good untill pressure builds up and then they leak and bleed off pressure.
[/QUOTE]
There is no rubber hose inside the fuel tank, at least not this one. The pump mounts directly to the pulsator, which mounts directly to the hard metal line.
FYI, this is all on a brand new Fiero Store sending unit setup.
We did, too. Even took a water hose and washed the tank out. It was horrible inside. The water coming out after rinsing was nice and clean.
Installed a new pump and screen and removed the pulsator due to bad seals in it. Not only did we have to replace the injectors, but the new Bosch pump failed, too. MikeMac then rinsed it with a commercial wash.
I plan to order the AC Delco pump, at worst I'll have one on hand for the next reclamation project. I’ll inspect the tank for contamination and corrosion when i change the pump.
There is no rubber hose inside the fuel tank, at least not this one. The pump mounts directly to the pulsator, which mounts directly to the hard metal line.
FYI, this is all on a brand new Fiero Store sending unit setup.
Ah, you still have a pulsator with the new setup. That's where most Fieros these days now have a short piece of hose installed instead... hopefully submersible hose.
Ah, you still have a pulsator with the new setup. That's where most Fieros these days now have a short piece of hose installed instead... hopefully submersible hose.
I figured it might be a year specific thing. 88 is definitely pulsator.
I figured it might be a year specific thing. 88 is definitely pulsator.
Actually, it's a fuel pump specific thing. The earlier years originally had pulsators installed as well. I forget the name of the style of pump from the factory, but a pulsator was required to reduce/eliminate pulses in the fuel pressure. The newer style fuel pumps don't produce these same pulses in fuel pressure, therefore pulsators have mostly become redundant. That's what I've read here over the years anyway.
Actually, it's a fuel pump specific thing. The earlier years originally had pulsators installed as well. I forget the name of the style of pump from the factory, but a pulsator was required to reduce/eliminate pulses in the fuel pressure. The newer style fuel pumps don't produce these same pulses in fuel pressure, therefore pulsators have mostly become redundant. That's what I've read here over the years anyway.
Matt Meyer dropped by, and he noticed something that i missed. The vacuum line running from the evaporatorative canister to the throttle body wasn’t connected to the boot on the throttle body. He said that will keep the canister from opening to the gas tank, and will cause a vapor lock. I haven’t connected it yet and done a test run. Probably get on that tomorrow.
Here is the problem...the vacuum line not working causes a vapor lock situation in the fuel lines, not the tank. That’s why loosening the gas cap didn’t make a difference. I have the Rodney Dickman stainless steel lines, and the bend was off just enough to keep the line from doing its job under vacuum.
Well, no.i put it all back together. Now, instead of it dropping out and sputtering randomly, it has a regular surge and drop pattern under hard acceleration. I didn’t have the fuel pressure gauge on it. Ill rerun that test tomorrow.
I reran the tests, still had the fuel pressure drop problem
I replaced the fuel pressure regulator with a spare used part, inspected it carefully, looked good. No change to the fuel pressure drops. I figured this left only the hoses or the pump.
I removed the fuel filter, and noticed some rust-colored gas pouring out and some rust in the filter. I finally got a borescope, and took this picture inside the fuel filter:
I dropped the fuel tank, and noticed rust on the inside of the tank, and sediment in the bottom.
I am assuming that the pump is getting clogged with that rust/sediment.
A crusty old car guy buddy suggested I use something he called "sloshing compound" to coat the interior of the tank and seal the rust. Is there a modern name for this, maybe a product recommendation?
[This message has been edited by fierobear (edited 07-13-2020).]
A crusty old car guy buddy suggested I use something he called "sloshing compound" to coat the interior of the tank and seal the rust. Is there a modern name for this, maybe a product recommendation?
I don't know if you've seen This recent post. Might do the trick!
Since avoiding to dropping the tank again, I would put in a new fuel pump as cheap insurance.
Yeah. I have a new one on hand.
My friend talked about some product that coats the inside of the tank with a paint/sealer type coating. Patrick’s link talks about an acid cleaner, but it doesnt seem to be a coating. Any ideas?
Edit: i reread the link, and it looks like what i need.
[This message has been edited by fierobear (edited 07-14-2020).]
My friend talked about some product that coats the inside of the tank with a paint/sealer type coating. Patrick’s link talks about an acid cleaner, but it doesnt seem to be a coating. Any ideas?
My friend talked about some product that coats the inside of the tank with a paint/sealer type coating. Patrick’s link talks about an acid cleaner, but it doesnt seem to be a coating. Any ideas?
Edit: i reread the link, and it looks like what i need.
Your friend is probably talking about a sealer known as "Kreem," or something similar. I've used it and do not recommend it for old, rusty tanks. It's basically like an acrylic paint. It does NOT remove the rust. It only paints over it, and surface rust is a poor foundation for paint. Over time it loosens up and the paint flakes off. It performs little different in an old, rusted tank (although it might be just fine inside a new tank). In comparison, phosphoric acid reacts with the ferrous metal to remove surface rust and, in essence, create a phosphate coating on the surface of the metal. A phosphate coating is very rust resistant. In the gunsmithing world this is basically called "parkerizing." I use phosphoric acid exclusively. Don't sweat it.
Ernie Here's a photo of the stuff I no longer use...Kreem...it's just a acryllic/latex-type paint/coating:
Don't sweat it. 
