low fuel pressure problem
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low fuel pressure problem I have a 95 LT1 in a 57 chevy it was running well I decided to do an off frame restoration so the motor sit for 3 years now that I have it back together I only have 45 lbs of fuel pressure when I had 58 and the pressure bledds off to 20 lbs in seconds and to 0 within a minuite of course the engine doesnt start. I pulled the injectors and had 2 dripping but not enough to cause the fast bleed I had another pressure regulator so I tried it but it was apparently bad as it wouldnt hold any pressure. no leaks that I can see could this be the regulator or injectors or just a bad fuel pump it was a new pump with only 1300 miles on it not sure of the model as it came with the stainless tank kit I ordered and help would be appriciated I have stock injectors and stock pressure regulator the engine ran fine before I parked it
Pete
Pete
How did you get 58 psi out of an LT1 stock FPR? They run at 43.5. An LS1 runs at 58.
Did you check for spark? If not, you may wish to troubleshoot that.
What do the plugs look like? Are they wet? If you are getting spark but they are wet and you are bleeding down pressure, you may have leaky injectors.
The initial bleedoff is not too alarming, but you should keep the overall pressure longer.
Did you check for spark? If not, you may wish to troubleshoot that.
What do the plugs look like? Are they wet? If you are getting spark but they are wet and you are bleeding down pressure, you may have leaky injectors.
The initial bleedoff is not too alarming, but you should keep the overall pressure longer.
After 3 yrs of sitting, I'm betting the injectors have either :
A. Dried out, and they are stuck shut.
B. The fuel in them, the rails, and even the lines, tank, has gone bad. It may turn to gell, or worse. The moisture in the fuel can/will rust the system.. Injs that are rusty are JUNK.
I find this situation in alot of the injectors I do..especially from the salvage yard engines.
+1 on Koolaid's comments!
A. Dried out, and they are stuck shut.
B. The fuel in them, the rails, and even the lines, tank, has gone bad. It may turn to gell, or worse. The moisture in the fuel can/will rust the system.. Injs that are rusty are JUNK.
I find this situation in alot of the injectors I do..especially from the salvage yard engines.
+1 on Koolaid's comments!
If you have any rubber line in the return, I suggest you try the following:
1. Prime the pump to build pressure.
2. Shut off pump & immediately squeeze off return line with a squeeze clamp to prevent any flow through the line.
3. Then watch the pressure.... if it still drops, it is not the regulator.
4. I would suspect the line inside the fuel tank between the sender & pump. These tend to deteriorate & 99% of the ones I see are using the wrong hose.
5. Also, as said above, LT1's should only have 43-46# fuel pressure, but I still suspect you have a problem if the pressure falls this fast.
6. Now, there is no reason the car should not start with 45# fuel pressure.
Since it is an LT1, I've seen quite a few optispark distributors go bad from sitting. You should be able to find a good diagnostic online to check this out.
1. Prime the pump to build pressure.
2. Shut off pump & immediately squeeze off return line with a squeeze clamp to prevent any flow through the line.
3. Then watch the pressure.... if it still drops, it is not the regulator.
4. I would suspect the line inside the fuel tank between the sender & pump. These tend to deteriorate & 99% of the ones I see are using the wrong hose.
5. Also, as said above, LT1's should only have 43-46# fuel pressure, but I still suspect you have a problem if the pressure falls this fast.
6. Now, there is no reason the car should not start with 45# fuel pressure.
Since it is an LT1, I've seen quite a few optispark distributors go bad from sitting. You should be able to find a good diagnostic online to check this out.
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I have all new aluminum tubing from the tank but havent been in the tank to see inside yet I put in new plugs yesterday most were wet when I pulled them I have power at the injectors and if I rewire the fuel pump to run constantly it will crank and run but runs rough and misses I suspect its losing pressure too fast to start if wired correctly and not holding enough pressure to fire the injectors or some are stuck maybe its got a bad rubber tube in the tank
Pete
Pete
Last edited by sneakypete1957; Feb 1, 2009 at 11:23 AM.
Plugs are wet, engine can run (although not very well). Line is new. Good information, which eliminates the ignition.
You might try draining the tank of the old fuel (next time use a fuel stabilizer) but I suspect the injectors. You most likely need to have them repaired (not very cost effective) or buy a new or used set.
You might try draining the tank of the old fuel (next time use a fuel stabilizer) but I suspect the injectors. You most likely need to have them repaired (not very cost effective) or buy a new or used set.
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when I took the car off the road for the restoration I drained the tank and taped up the openings but the line in the tank still could have dried out. would the injectors cause the fast bleed off of fuel pressure?
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Thread Starter
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Problem solved I replaced the injectors today and pressure now holds at 43 lbs and 30 mins later its at 20 lbs cranks and runs smooth thanks everyone for all your help esp Koolaid Kid I'll post some new pics afer we get the new paint beffed and chrome polished
Pete
Pete
