Fuel pump question..... Not a GMT400 but still GM.

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DeCaff2007

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Sorry I keep posting non-GMT400 questions, HOWEVER, there's a serious lack of support (meaning no forums, and I don't do the FB garbage) for what I'm working on.

Long story short, I'm converting my Wife's 67 Buick Special from a junk 2bbl carb, to a Holley Sniper EFI... in hopes of a very large increase in reliability.

So, here's the skinny. The [absolutely worthless] factory fuel system had to be junked and replaced with this: https://www.efisystempro.com/fuel-s...odules-chevelle-malibu-el-camino-64-67-12-302.

Fuel pump is wired into a relay that comes with the EFI harness. A switched 12.5V triggers the relay and that fires the pump. Easy, right? Not really. I'm only getting 11.8 ~ ish volts out of a brand spanking new AC Delco battery. I thought, ok, maybe it's a bad relay so I tested that separately. The relay is fine.

With that, since I can't get the relay to trigger when it's in the car, I JUMPERED the two relay terminals (in the wiring harness) to act like a relay that's turned on. Fuel pump INSTANTLY fired up and pegged my fuel pressure gauge past its 100 psi max reading.

How is that possible? There's a regulator in the pump and on the EFI unit. Can a fuel pump even go that high? I don't want to go returning a very expensive and very proprietary fuel pump if I don't have to. Maybe a bad fuel pump tester? The last time I used that tester was to verify the correct PSI for the 2bbl carb on this same vehicle. It worked fine, although it only needed 5 PSI, which it held nicely.

I'm at a loss here. Can an electric fuel pump seriously support 100+ PSI?
 

Schurkey

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I'm converting my Wife's 67 Buick Special from a junk 2bbl carb, to a Holley Sniper EFI... in hopes of a very large increase in reliability.
The original '67 fuel system was very reliable. It's unlikely to get better with more electronics.

The new fuel-injection system may be "as" reliable, if all the supporting wiring, and the installation workmanship is adequate.

So, here's the skinny. The [absolutely worthless] factory fuel system
It wasn't worthless when it was in decent condition.

had to be junked and replaced with this: https://www.efisystempro.com/fuel-s...odules-chevelle-malibu-el-camino-64-67-12-302.

Fuel pump is wired into a relay that comes with the EFI harness. A switched 12.5V triggers the relay and that fires the pump. Easy, right? Not really. I'm only getting 11.8 ~ ish volts out of a brand spanking new AC Delco battery.
If the battery only provides 11.8 volts no-load, it's faulty or it's undercharged.

Charge battery, re-test. A fully-charged battery should have 12.6--12.7 volts. 11.8 volts is pretty close to "dead".

Or do you mean there's wire harness problems between the battery and the relay that create massive voltage drop?

I JUMPERED the two relay terminals (in the wiring harness) to act like a relay that's turned on. Fuel pump INSTANTLY fired up and pegged my fuel pressure gauge past its 100 psi max reading.

How is that possible? There's a regulator in the pump and on the EFI unit. Can a fuel pump even go that high? I don't want to go returning a very expensive and very proprietary fuel pump if I don't have to. Maybe a bad fuel pump tester? The last time I used that tester was to verify the correct PSI for the 2bbl carb on this same vehicle. It worked fine, although it only needed 5 PSI, which it held nicely.

I'm at a loss here. Can an electric fuel pump seriously support 100+ PSI?
Depending on the pump...sure. Most won't go that high, but either you've got an inaccurate gauge or that particular pump can push 100+ psi.

Holley claims the pump is regulated to 58 psi inside the tank. Yours apparently has a faulty in-tank regulator.

You should be contacting Holley tech support. This is not "still GM", these problems are entirely aftermarket except perhaps the battery-voltage issue.
 

DeCaff2007

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I was very much hoping that that wasn't the case. I've heard that Holley tech support is trash.
 

DeCaff2007

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I just wanted to post an update to this... I've solved the issue of the relay not turning on. It's a long story, but suffice it to say that I had to go through the Sniper EFI programming wizard and enter the info it wanted, let it do it's thing, then cycle the ignition. Fuel pump now acts as it should... through the relay. Damn computers. This car was never meant to be like this....

Seems I've fixed the few leaks there were, too. The whole car has 3/8th fuel line, EXCEPT for the line that would come from the factory mechanical fuel pump, to the carburetor. That line is 5/16ths. Not anymore lol.

I also had to run some 3/8ths rubber fuel hose to connect a few hard lines in places. Let me tell you... don't ever order from EVIL Energy. Their stuff fits too loosely. That is all.
 

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I also had to run some 3/8ths rubber fuel hose to connect a few hard lines in places.
That hose better be rated for the 100+ psi your system is capable of.

Which is probably well-beyond what typical "fuel injecton" hose is rated for. (Regular "carburetor" fuel hose will last about thirty seconds.)

"I" would be using steel-braid-over-Teflon (PTFE)-liner hose, with the 37 degree industrial fittings as needed.
 

DeCaff2007

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That hose better be rated for the 100+ psi your system is capable of.

Which is probably well-beyond what typical "fuel injecton" hose is rated for. (Regular "carburetor" fuel hose will last about thirty seconds.)

"I" would be using steel-braid-over-Teflon (PTFE)-liner hose, with the 37 degree industrial fittings as needed.
@Schurkey, relax there, high speed. It's EFI rated hose. That Pump is SUPPOSED to be internally regulated at 58 - 60 PSI.

We are going to attempt a first start today. If that goes south, I guess I'm going to HAVE to call Holley tech support :rolleyes:.
 

Pro439

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So what I read on the Holley website for the sniper installation is that the fuel is regulated on the outlet port? Don’t know if that is what your instructions say or not. And I agree the rubber hose is ok but I don’t know what the longevity will be. It would definitely benefit you to get braided line for gasoline as they make it for many different fluids nowadays. And I can understand your frustration with the whole thing if you don’t know carburetors this is the simplest way to go. Holley tech is not bad I’ve had to use them as I’ve swapped out stock stuff for there stuff and am doing an all efi swap intake throttle body etc on a 97 bbc but running the stock computer. Luckily I know how to do carburetors as well. Hopefully the rest of your install goes smoothly
 

Erik the Awful

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The website @DeCaff2007 linked says the fuel pump is supposed to be regulated within the tank at 58psi. There's your problem, and yes, Holley's tech support is nearly non-existent in my experience.

I used a Vortec fuel pump in a TBI sending unit to feed the Sniper on my '89. Works great.
 

DeCaff2007

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The website @DeCaff2007 linked says the fuel pump is supposed to be regulated within the tank at 58psi. There's your problem, and yes, Holley's tech support is nearly non-existent in my experience.

I used a Vortec fuel pump in a TBI sending unit to feed the Sniper on my '89. Works great.

This, exactly!

How exactly did you pull that off?
 
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