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edelbrock fuel injection

J

jmeti000

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k i have written on this before and got much help and hope it continues. i have an 88 chevy blazer with im guessing a 90 engine in it and edelbrock port fuel injection. ive replaced everything (yes everything) and am having a problem with my fuel pressure. the machine it was hooked up to says it has about 20psi on the fuel rail and it runs like crap...but when the pressure is bumped up by the machine to about 40psi it runs beautifully. so, my question is would that be related to the fuel pump or the pressure regulater. i have replaced both, and the fuel pump that i was given was for throttle body injection and the psi is WAY less than what port injection is supposed to be, but like i said, i dont know weather thats related to the pump or the pressure regulator. PLEASE HELP ME AGAIN!!!
thankyou
jacqui
 
TBI runs at 12-14, MPFI runs at 40-60psi. You need a pump designed for the MPFI, not the TBI. Put in a MPFI pump and it should be good to go. Edelbrock sells pumps designed for this purpose. I have a supplemental pump since I have dual tanks. Uses the stock tbi pumps in the tanks and then the edelbrock pump on the rail which raises the pressure. I believe the single tank setup is a new in tank pump. IIRC the part numbers are 3580 and 3581, but I dont remember which is for what pump. Good luck.
 
Same results, cause is still unknown for me.

MPFI conversion, with the higher pressure pump. It had been running great, but then perhaps after running the tank to low, I might have clogged my pump? I changed out the fuel filter, but that did not help.

I am running around 18psi at the fuel rail when it should be around 35-45psi while running.

What I cannot figure out as of yet is if it is the fuel regulator (all of this which is fairly new) or a faulty pump or pressure sensor.

Anyone have the best bet of which item it is? Both the pump and the fuel injection setup are quite new.

Thanks!
 
gm is great with the pumps. the same size bodys but bigger pressure is built in the pump. so get one for a gm car with mpfi /tuneport. will clip in to your sender no problem. and you said you swaped in a new tbi pump. that wont work like stated even with a regulater. as it only will do 20ish max.
 
I should clarify, the pump I have is a high pressure (like 65psi max) edelbrock or GM. The previous owner (a friend of mine) gave it to me when I piece-mealed the truck together. He had the pump on another MPFI kit truck and it also worked fine then.

Results appear to be either electrical or in the pump / hose area (internally). I suppose pressure would not build up high enough even if the regulator was working properly, if the pump is not working right. Note that pressure remains steady at idle. It dips a little when opening the engine up.

Thanks for the responses and part number!

I will update once I nailed it down exact.
 
Just a quick update.

The problem I had was a burst hose in the tank. There is a small hose that sits between the fuel pump and the pickup hardline that had a vertical slit in it. The slit kept enough pressure to idle, but not drive.

I pulled the pump, put a better EFI fuel hose (note that you need EFI hose, not just fuel hose), metal clamps and walla, 40-50 psi!

Problem fixed with a .10 part + a little bit of labor.

(now, on another issue, I have too much fuel pressure. 90 psi anyone?)
 
boxxerace said:
(now, on another issue, I have too much fuel pressure. 90 psi anyone?)
Click to expand...

Try adjusting your regulator or replacing it with the right PSI if it is non adjustable.
 
I will go and check.. it is the unit that comes with the edelbrock efi setup I have... made by another company however.

I am going to check and see if it is adjustable (beside through the vacuam hose that goes to it).

thanks for the suggestion!
 
Edelbrock tech emailed stating that a failing regulator would result in lower pressures and not high pressure. He stated to check for a line being pinched.

Well, I have yet to check, but I have not done anything in the last few days that would pinch a line + besides hardlines and hoses at the tank, I have stainless lines that are unlikely to get pinched.

I am going to try undoing the vacuum line and see what the pressure sits at.
 
sure the gauge is reading correctly? I couldnt even see how a pinched line would cause high pressures on the rail....
 
Edit: I should note that the regulator is not adjustable.

Well, I cannot be sure other than to replace the 45$ critter. The gauge is about 2 months old and seems to have been working just fine. It showed me my issue regarding low fuel pressure and then when fixed, it maintained around 40 psi. As of now, after starting it, I saw it rise from 80 - 90 psi.

I am going to go out and check for pinches right now. I should also add that I put a new fuel filter in a few months back (on the feed line) so I doubt its dirt. 90 psi is alot!

Do you think it is even safe to drive?

(headed out to check out, will look for your response in a minute... Thanks in advance! )

---------------------------------------

Edit: (double posts are lame enough). So, no pinched hoses (duh) and nothing out of the ordinary from what I can tell. The gauge drops now to about 75 psi when running (and while it did not want to start and seemed to be running rich, the starting issue has happened before). Anyhow, when manually increasing engine rpm, the needle to the gauge jumps down every so often, like quickly dropping 10 psi before rising back to the 75psi. Maybe I do have a fuel gauge going bad? How weird is that?

unfortuately, a fuel pressure gauge is not a common tool in the garage or for rent. I guess I will have to dig another up.

Time for a test drive and checking pressures along the way. Lets hope I dont go KABOOOM!
 
Last edited:
check your return line

boxxerace said:
Edelbrock tech emailed stating that a failing regulator would result in lower pressures and not high pressure. He stated to check for a line being pinched.

Well, I have yet to check, but I have not done anything in the last few days that would pinch a line + besides hardlines and hoses at the tank, I have stainless lines that are unlikely to get pinched.

I am going to try undoing the vacuum line and see what the pressure sits at.
Click to expand...

I'd check your return line and make sure it is not pinched. The regulator probably can't lower the pressure if it can't redirect the extra fuel back to the tank.

Tom
 
If it were the return line pinched/pluged or otherwise restricted the presure would raise.

Drop the tank and clean the sock, replace the hose, test the pump.
 
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