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View Full Version : GM mechanics: 7400 Vortec fuel pressure


Beer-30
10-21-2006, 06:54 AM
I know some of you are either current or X-GM mechanics. So here goes.
My dually is a '98 with the 7400 Vortec. I have a whole deluxe OTC fuel pressure test kit with all the couplers and such. Although one only needs the shrader valve connector. Anyhoo, I have been going through everything before this next season. I just did MSD plug wires and new AC replacement plugs. Now, I want to check the fuel pressure and make sure the pump is still along for the ride.
I never did buy a shop manual for it. What pressures should I see? Idle with vac connected (what's the normal pressure as it runs down the road) and also with the vac line off of the regulator?
I'm going to go ahead and replace the HEI module, cap, rotor, and coil - DUI Ignition has a bitchen replacement upgrade set for this specific application. I am now nervous about the pump, as the truck is 8 years old next month, but only has 78,000 miles. I will only have it until about July of next year, so I am hoping I don't end up doing the pump. I just want to see what pressure(s) it is putting out or not putting out.
HALLETT BOY
10-23-2006, 08:34 AM
56 - 62 lbs
Beer-30
10-23-2006, 10:33 AM
Wow. Ok. Will check and report.
Thanks.
Trailer Park Casanova
10-23-2006, 03:57 PM
Some fuel pumps have bad check valves causing a drop in pressure and hard cranking when starting.
Beer-30
10-23-2006, 06:06 PM
I am mainly worried about it's health. It's starts right up, no problems there. It is probably fine, but it is time to keep an eye on it. 8 years old, 78,000.
502 JET
10-28-2006, 05:52 PM
The pump on my 97 suburban 7400 Vortech went bad with 118,000 miles. I replaced the sending unit too because it was rusting away.
dicudmore
11-07-2006, 02:16 PM
I am mainly worried about it's health. It's starts right up, no problems there. It is probably fine, but it is time to keep an eye on it. 8 years old, 78,000.
Beer--you know as well as I do that you can't predict the life expectancy of a fuel pump. Good pressure today doesn't mean that it will have pressure tomorrow :wink: If it passes the start test then go with it--when it doesn't pass the start test--give it the kick the gas-tank test :D
Beer-30
11-07-2006, 03:21 PM
Beer--you know as well as I do that you can't predict the life expectancy of a fuel pump. Good pressure today doesn't mean that it will have pressure tomorrow :wink: If it passes the start test then go with it--when it doesn't pass the start test--give it the kick the gas-tank test :D
Oh, I know. I just remember the TBI caper on here with the motorhome pissing and moaning uphills. He checked ign and all and was still popping. Checked the fuel pump pressure and it was half of normal. It is running perfect, but I can just see that damn thing going belly-up at about Zyzyx Road next year.
I dug around back there, but couldn't get to the regulator. Showed 54 psi at idle. Rock stead. Gonna leave it till it quits or I get rid of it (late next year).