EFI conversion: the good, the bad and the ugly.

rocket dawg

Veteran Member
May 5, 2015
566
Grand Rapids Mi
Here's my situation. I've added Holley Sniper EFI and it's been good so far. If I had to do it again, I'd opt for the inline exterior fuel pump. My friend has this and it's a loud pump for sure, but it has its advantages. I installed a new gas tank ( 79 T/A sbc 400 mota ) designed for the in tank fuel pump and I've had my issues with it. I over tightened the fittings and cracked a $300 plus fuel pump= leak ( my fault) dropped gas tank. Next time I was gun shy and didnt tighten enough= leak another gas tank drop. Fuel line routing problems and pinched fuel lines- tank drop and hammer the trunk floor up in a few areas for added clearance. These gas tanks dont leave any wiggle room. Fast forward 1.5 years and everything has been good. I fire the car up this week after storage and gas leaking on the floor when car is running. WTH! Yet another gas tank fuel pump issue. When I have the tank out this time, I'm thinking about cutting an access panel in the trunk floor. Has anyone done this? If so , post some pictures. thanks. Going out to siphon gas yet one more time.
 

acmanted

Veteran Member
Mar 6, 2011
115
Oak Harbor, Wa
Feel your Pain, I’ve had a few issues with my tank/ EFI set up. IMO take the time it takes to do it right. You will solve your problem and you will be happy that you didn’t cut up your car out of frustration. Good luck
 

CorkyE

Veteran Member
Lifetime Gold Member
Nov 4, 2004
11,703
Ringgold, GA
What in tank pump do you have? I'm using a Holley 12-304 that just drops in the stock tank, feeding a ProFlo 4 system. I had to retighten a front fitting, but nothing else. I've had several external pumps with carburetors, not with efi, and they're loud.
 

krabben1

Veteran Member
Lifetime Gold Member
May 16, 2007
8,429
( . Y . )Delco
I have the sniper inline external pump on my camaro,and it is noisy.
I have the internal tank pump sniper on my 67 chevelle and its been fine,and quiet,except for the on again/off again fuel sender issues.
I used a holley sniper retro fit tank,which was pretty nice,especially for the money.The intank pump was expensive,but I like the fact that it didnt require a return line.I did have a line blow off at the tank,holley made the fuel pump feed lines as per spec for a 67 chevelle,which is 5/16"(dumb)when they require a 3/8" for their product.So I just double clamped it and its been good.No other leaks so far.
I would drop the tank,and double clamp it all.
 

rocket dawg

Veteran Member
May 5, 2015
566
Grand Rapids Mi
The tank is still in the car as of this morning. Gas is drained out, about 18 gallons worth. Siphon hose is very small so it takes about 25 minutes to fill a 5 gallon can. I was working on other stuff ( distracted) and the gas can over filled and down the floor drain it goes. Maybe a gallon. So out comes the degreaser and hose. I dont know what is leaking yet. Later today or tomorrow I'll know. The fuel pump has 6 or 8 small bolts with a gasket that holds it in and it has a return line. I'll have to look at my notes to find the part number. I routed the hoses so that I have enough to drop the tank with the hoses and wires still intact. So the plan is drop the tank, add some gas to it, turn key on and locate the leak. Yeah. I'm very hesitant to cut metal with all the sparks anywhere in that area. I believe this is the tank and pump kit:

Holley Sniper 19-140 - Holley Sniper EFI Conversion Fuel Tanks​

https://www.summitracing.com/parts/sne-19-140/make/pontiac/model/firebird/year/1979 The part number for the pump isnt listed with the tank kit. But I had to order just the replacement pump once. Summit figured that out.
I have enough hose so that I can cut it, install a new fitting ( if needed) and re install. Once a fitting is on the hose, its impossible to remove it w/o destroying it. A loose clamp or fitting is probably the cause. An access door sure would be nice at this point. The stock tank goes in and out fairly easy, this new tank seems a bit larger so I have trouble getting the strap bolts tightened up. 1/2 inch longer bolts may help this time. Overall, I like the Sniper EFI system, car runs great. The hand held screen died last year. Holley sent a new one free of charge. ( $308 cost) .
 
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rocket dawg

Veteran Member
May 5, 2015
566
Grand Rapids Mi
Dropped the tank, everything still hooked up. Turned key on and no leak. Okay add some gas just to make sure its pushing fuel and again no leak. So we have it narrowed down to the return line. Check clamp on pump and it's as loose as the neighbor lady. So I'm told. I have no idea what return line pressure is supposed to be. That fitting is now double clamped. The only way to check is to fire up the car which is possible, but I'm 99.9 % sure I found the leak. An access panel would have been an ez fix. About 3 minutes total. But making an access panel would require hours of fabricating to make it look right. In the long run, adding EFI is a very good upgrade.
 

rocket dawg

Veteran Member
May 5, 2015
566
Grand Rapids Mi
I've asked a few people and 10 to 12 psi is their best suggestion. For a return line. Looking at the top of the tank, and the return line was the culprit. I'll check with the Holley Sniper website to confirm pressure. I'll keep ya posted.
 




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