jagevileye21

iTrader: (3)

I have a 91' Z28 with an 350 LT1.

I have changed everything I could possible think of.

Fuel Pump
Fuel Filter
New Injectors
Stainless Braided fuel lines.
Fuel Pressure Regulator. 1yr ago

Fuel is getting up to the rail via (inlet line). There is fuel in the rail, however no fuel is coming out of the regulator on the return line side. Correct me if I am wrong but with a fuel pres. reg valve stuck open fuel would just flow back to the tank with little or no pressure present. The only problem with that is that I am getting nothing on the return side and I have no pressure. If the valve was stuck closed pressure would build up and if it did not open it would have too much pressure.

Since the fuel seems to be going nowhere (staying in the rail) I should have a nice amount of pressure in the rail. Especially since none my injectors are leaking. Thats not the case the fuel guage reads no pressure 0psi.

I don't have any leaks. None of my lines are clogged. The rail is not blocked or clogged. Nothing is restricting the flow of fuel.

I do notice a strong scent of gas at the vacuum line connecting to the intake. However, I don't see any leaking from the vacuum port itself on the fuel pres. regulator.

If anyone has any suggestions that would be great.

Thanks,
Jay

kowboy59

iTrader: (8)

i know this may sound weird, but try using another gauge. It could be a bad gauge.

Darkshot

iTrader: (4)

Check to make sure the female fitting on the gauge is activating the little pin inside the schrader valve. Mine did that after I installed a new pump and I temporarily freaked out until I figured it out.

jagevileye21

iTrader: (3)

I was thinking that the guage could be bad. I will try another one later. What if it still does not have any pressure? Suggestions?

Darkshot

iTrader: (4)

In the meantime you could try pushing in the pin on the schrader valve manually and see if fuel shoots out. Be very careful though so you don't start a fire.

Sorry that's all I got I don't know the LT1 very well.

jagevileye21

iTrader: (3)

Fuel does come out when I push in the schrader valve. Althought not with that much pressure. Seems kinda weak.

SpitotRs305

when the key is turned on the LT1 fuel system primes pretty much like the TPI system pushing in the valve anytime within 20 minutes of operation should spray fuel... normally hits the underside of my hood... ******* enjuneering thats when you have enough pressure if it isnt i would first check flow by removing the feed and see how long it takes to fill up a pint should be fairly quick like 10-15 sec.. if you have flow there i would start looking at your FPR

jagevileye21

iTrader: (3)

The fuel pressure guage that I'm using is working correctly. I tested it on another car.

With that being said, I still have no fuel pressure.

I disconnect the feed line from the rail to find out that little or not fuel is getting to the rail. Afterwards I disconnected the feed line coming from the tank to see if any fuel was actually coming from the tank. No fuel came out.

Now I am completey pissed. After dropping the tank three times and replacing three fuel pumps. I am still in the same position I started. What could be causing this problem?

I hear the pump turn on.
I am getting 12V back to the pump.
I have over a half tank of gas.
I installed the strainer correctly.
When I had the tank down I made sure the feed line was not clogged.

If anyone has any suggestion let me know. I hate taking my car to the shop.

Thanks,
Jay

afremont

Sounds like you've pretty much proven that the pump is not pumping. You hear it run, but absolutely nothing comes out of the tank? Even my pump after sitting for six years would make 10-15psi at the rail. When was the last time you dropped the tank and replaced the pump with a new one? Only other thing I can think of is that it's possible the pump is running backwards, especially if it's an aftermarket type.

By backwards, I mean the power wires could be reversed. Something to look into. How old is this pump again?

jagevileye21

iTrader: (3)

I replaced the pump last friday with a stock replacement from Murrays. The odd thing about is that some fuel was present in the rail. But now no fuel is flowing at all.

pandin

Check the lines in the tank, a split/loose one would just dump fuel back to the tank.

ssean92

iTrader: (10)

I know this sound bad but is it wires right the pump that is, it will run backwards, also you might try priming the line, take feed line off the rail and turn the key and see how much gas comes out. I had to do that after i put my Walbro 255 in, was doing the samething

ghettocruiser

iTrader: (4)

Ide be tempted to unhook the line from the rear of the filter, attach a hose to it or stick it in a bucket, and turn the pump on. Fuel some come out at a pretty decent rate.

If it doesnt, you need to recheck the pump install. And also do a voltage test at the wires to the pump. That wiring can get weak because of the amount of current that goes through it during the life of the vehicle. Thats why a lot of 4th gen guys even are using a hotwire kit to make sure full voltage gets to the pump.

I know you said you are getting 12v to the pump, but where did you check it? At the actual terminals on the pump? If the pump is pumping, and you have no blockages, there is no other reason not to get full psi at the rail. I guess if the regulator is messed up..but I didnt ever mess with mine so Im not much help with them.

J.

jagevileye21

iTrader: (3)

I reversed the wires on the pump and now a good amount of fuel is making it up to the rail. Fuel pressure seems as if it wants to build but then it drops.

I unhooked the line coming from the tank and it filled up a 20oz container fairly quick. 10-12secs.

I checked the voltage at the connector and on the wires after the connector. 12v+

I tried priming line there is alot of fuel in the coming thru it. I will try to replace the regulator later and let you guys know.

Thanks,
jay

ssean92

iTrader: (10)

so the wires were turned around, it still isnt getting pressure and staying? also check to see if any of the injectors are leaking

87nosirocz

you may have losened the fuel pump intake in the tank and its pulling air with the fuel.

jagevileye21

iTrader: (3)

None of my injectors are leaking. The fuel pump was very secure in the pulsator during installation. Im still banking on the fuel pressure regulator being bad. There is alot of fuel getting up to the rail seems almost normal.

jagevileye21

iTrader: (3)

I haven't had a chance the get another regulator yet, but my regulator is just over a year old. I disconnected the inlet line from the rail & placed it in my 1 gallon gas container. I then hooked the fuel pump up to 12V and the container was full in less then a minute. Afterwards, I hooked the line back up to the rail and connected the pump to 12V again. Still no pressure. If the regulator was stuck closed it would built a lot of pressure. If it was stuck open I would have fuel flowing thru the return line back to the tank which is not so.

Is it possible my accel injectors could be stuck open.

The reason I hooked the fuel pump up to 12V directly is so I would not have to turn the key, so I wouldn't have to activate the injectors.

I have no leaks whatsoever. I need to locate another rail and injectors.

Jay

ssean92

iTrader: (10)

did you remove the regulator to see if gas comes out of the hole were it goes? if it does it is the regulator, if not I would look at the fuel rail, and you need to hook the pump back to a ignition source, you will burn it up fast

afremont

In the engine compartment, you can clamp off the rubber return line (between the fuel rail and the hard line on the chasis). This will prevent fuel from being able to return to the tank. If you can build pressure then, you will know for sure it's the pressure regulator. Don't over do it though. Your pump is probably strong enough to damage the pulsator if you let it build too much pressure. I use a jumper wire from the + terminal of the battery and the fuel pump "priming" connector on the firewall to make the pump run without having to take my eyes off the fuel pressure gauge.

pandin

Sounds to me like the short line inside the tank is split. This will be your exact symptom. Lots of flow (volume) no pressure. The split will release the pressure but still flow 100 %.

Completely remove your regulator diaphragm, spring and all, just the open hole. Make a temporary gasket out of a cracker box (open a hole in the center) and replace the cover only. Bump your fuel pump on to see if there is any gas in the return line. If there is flow, then start pinching down the return line slowly. Fuel pressure should start to show.

If you still have no pressure but good flow, pull the tank and look at the line down stream from the pump. This is the only place the fuel can get back to the tank without building pressure.

Also double check the shrader valve release, the pressure may be there, but the gauge can't see it. I have to remove the check valve to read mine.

The fuel is not leaking past/through the injectors, holes are too small and the engine would be full of gas (1gal/1min). If the rail is plugged, removing the regulator will not change the no fuel in the return line.

This is a common problem when the fuel pump is upgraded. Usually if the clear line is used it splits or the old line just gives up. Be sure to use higher pressure FI hose not carb hose.

You can do a bucket test with everything out, but use kerosene not gas, no boom.

jagevileye21

iTrader: (3)

When I open my gas cap I have alot of pressure and hissing. I will take the regulator off to see if any fuel flowing. What clear line are you talking about?

pandin

Sometimes the fuel pump kit will include a clear line to attach the pump to the pressure line, these are not reliable.

When you are checking, have someone listen at the tank (cap off), while the fuel pump is running, to see if you can hear fuel splashing (split line).

afremont

Have you tried clamping the return hose under the hood to see if pressure builds? It's what the FSM says to do. It's easier than dropping the tank to look for a split line.

jagevileye21

iTrader: (3)

I got a new rail and regulator today. After installing both, I hooked the fuel pressure guage up. I energized the fuel pump a few times. The pressure went up to 10psi and fell to 0 psi after the initial two seconds. I did this a couple more times only to get the same results. Just to see if the pressure would be constant or not I hooked the battery up to fuel pump. The pressure went up to around 15psi max and the leveled out around 10psi. Now on leaning towards a bad line inside the tank. (But how the in the world would that happen). I tried clamping my return line but its kinda hard with braided lines because they dont go back to there original shape. Anymore suggestions would be helpful??? I also found another set of injectors. Probably try them tomorrow.

Thanks

pandin

In-tank Fuel Pump Install Tips

• Inspect your tank VERY carefully. If there is ANY dirt in there, clean it out. If there is any rust in there, you must take care of that problem. If you need to clean the tank, you should also clean the fuel lines. The main cause of early fuel pump death is dirt in the system. A pump that dies due to dirty fuel can not be replaced under warranty.
• If you need to use a piece of fuel hose inside your tank, be sure it is SAE J30R10 spec hose. That hose is high pressure fuel hose that was designed to be immersed in fuel. DO NOT use fuel hose that is designed for inline use only [SAE J30R9]. It will not survive inside the tank.
• Be careful when handling your new fuel pump. The outlet nipple can't be supported because a hose usually has to go over it. If you aren't very cautious, it will break off. That, unfortunately isn't a manufacturing defect and is not covered under warranty. I have received stories of folks that pick up the box quickly and end up slinging the pump across the room. Now, I put tape on each end of the box in an attempt to lower the pump casualty count. I have heard from folks that have tried to epoxy that nipple back on the pump. No one has had success with that repair method. If you drop your pump and it ends up looking like the one in the following picture, you are not alone.
  
  
• Be careful when removing the rubber cap from the outlet. The pump's outlet nipple has a retainer on the end of it that holds the check valve in the end of the pump. That retainer also serves as a shoulder to prevent the hose from coming off. If that retainer comes off, that is bad. Most of the time, that retainer won't stay on if you try to put it back. It usually comes off and lodges itself in the hose, thus becoming a flow restrictor. After that, the check valve will probably come out, and your system won't hold pressure. The best way to avoid all those nightmares is to cut the rubber cap off the outlet instead of pulling it off. Below is a photo of a pump with a missing retainer ring. The check valve is that white piece in the end of that nipple.
  
  
• Many GM vehicles, and a few others, have a small can that attaches to the outlet of the pump. That is a pulse damper. It is designed to even out the pressure pulses from the fuel pump. Below is a photo of a typical GM pulse damper. Both ends look like the end that is shown. The pump pushes into one end and the supply line tubing pushes into the other end. Notice that there isn't really a way to put a hose clamp on that connection. That is a source for a leak under high-pressure conditions. We suggest that you remove any pulse damper and use a piece of high pressure fuel line and a couple good clamps.
  
  
• Some of the DSM installations have been less than a total success on their first attempt. I have received notes from a couple owners that have experienced a "cutting-out" behavior above 5000 rpm after the install. The problem appears to be the o-ring in the install kit is not fully sealing in the original pump hanger. The union between the pump and the original hanger MUST be VERY snug. If there is any play in that connection, it will leak. If the o-ring in your install kit is not snug, try the o-ring that was with your original pump, or cut off that flared section of the original fuel line and use a short piece of high-pressure fuel hose and clamps.

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jagevileye21

iTrader: (3)

So you think I should remove that pulse damper?

afremont

I do; I don't like how it seals.

pandin

The pulse damper is made for a certain fuel pressure range, anything above that the damper is just useless. It has to do with harmonics, between the pump vanes, length of pipe, and the injector pulses. Some people get a tick from the regulator that annoys them. Dampers work like an air tank on a water system to keep the pipes from banging when the water valve (fuel injector) is slammed shut (spikes the water pressure). Also know as accumulators.

jagevileye21

iTrader: (3)

None of my fuel pumps have that check valve. Could this be may problem? Also would the pump running backwards hurt my pump?

Thanks,
Jay

ssean92

iTrader: (10)

if it was running backwards you wouldnt get fuel, or are you talking about before you changed the wires

jagevileye21

iTrader: (3)

I was talking about before I changed the wires.

ssean92

iTrader: (10)

it might have ,but if you are getting fuel then it shouln't be an issue..... there is something strange going on

jagevileye21

iTrader: (3)

I took the tank down again. Removed the pulsator and damper. Replaced it with a hose and clamps. Hooked up the fuel pressure guage. It read 45psi after a turning on the pump twice. Pressure leveled out about 40 psi. The car started on the first try. Thanks for all the help and advice.

Jay

pandin

Was the line split or was damper just leaking real bad?

jagevileye21

iTrader: (3)

The damper was leaking it didn't seal to tight.