Fuel Pump Replaced - where'd I go wrong?

[SuperSpore]

1991 Chevy c1500 short bed 7.4 with a 25 gallon tank.

Suddenly Stopped idling properly, acting like starved for fuel, wanted to die. fuel pump fuse is good.
Swapped the entire fuel pump assembly for a new delphi/ac delco.

Pump does not prime, no start. There is no pump priming process for these, correct?
Anything I might have missed?

If accidentally I swapped the fuel delivery and return lines, how do I distinguish one from the other? any fuel pump damage if I did?

Another possibility is I installed the wiring plug in reverse, but I'm not sure it would go in that way. (I did reinstall the ground.)

Last option will be to swap the fuel pump relay.

Any ideas are appreciated.

 

[delta_p]

There's got to be some priming operation or there won't be any pressure to start the truck. Normally there's about a 2 second prime, maybe up to 20secs if the line is totally dead or can't build pressure?

Hit this link and get the 1991 manuals. There's one for the fuel and emissions systems. https://www.gmt400.com/threads/88-95-service-manuals.43575/

 

[Ehall8702]

Cycle key two or three times without starting engine , and try and start engine after that and should have no issue starting after that. I replace pumps and complete lines about twice a week at the shop and have never had to cycle key more than twice and engine fires directly up.

As far as mixing feed and return lines, u would have to really try and booger it up to do that. Feed is 3/8 and return is 5/16. Usually the threaded lines that screw to pump are rusted to crap up here, we end up cutting the rubber and putting a barbed fitting in and even the hoses r way different sized.

If u just put in a new pump ( not replaced the complete sending unit) I would be checking wiring if u can't hear pump running or the piece of rubber line between the pump and the sending units feed tube. One more thing to check is if it was one that you had to upgrade the fuel pump plug , recheck your wiring and always remove the ground, clean the frame and put it back.

It's a PITA but you gotta pull everything back apart if u can't easily find the issue or it's just not a fuse or something dumb.

 

[SuperSpore]

Thanks guys for your responses - I appreciate the the manuals Delta, and thank you for the explanation on the lines Ehall.

I just swapped the relay and it did start. =-)
Unfortunately, it's idling as bad as it was to begin with - but at least it has a new fuel system. ha... ha. ;-)

 

[Steve A]

Check the pressure regulator on the TB just behind the injectors. Seen several leaking, a few so bad that #1 plug was fouled out. Standard Motor Products used to list a rebuild/reseal kit that was priced pretty reasonably.

 

[Schurkey]

Suddenly Stopped idling properly,

Have you verified the plugs, plug wires, cap, rotor, ignition timing, cranking compression pressure, and spark intensity?

Have you checked fuel pressure?

Have you run a cylinder balance test to discover weak or dead cylinders?

Connect a scan tool, look for anomalies in the data stream--what is the short- and long-term fuel trim numbers? MAP sensor providing reasonable readings? Coolant temp sensor accurate? TPS and IAC working properly?

 

[Ehall8702]

Cycle key two or three times without starting engine , and try and start engine after that and should have no issue starting after that. I replace pumps and complete lines about twice a week at the shop and have never had to cycle key more than twice and engine fires directly up.

As far as mixing feed and return lines, u would have to really try and booger it up to do that. Feed is 3/8 and return is 5/16. Usually the threaded lines that screw to pump are rusted to crap up here, we end up cutting the rubber and putting a barbed fitting in and even the hoses r way different sized.

If u just put in a new pump ( not replaced the complete sending unit) I would be checking wiring if u can't hear pump running or the piece of rubber line between the pump and the sending units feed tube. One more thing to check is if it was one that you had to upgrade the fuel pump plug , recheck your wiring and always remove the ground, clean the frame and put it back.

It's a PITA but you gotta pull everything back apart if u can't easily find the issue or it's just not a fuse or something dumb.

Sorry just happened to re-read post, I was talking about a gasser, doubt it's same steps for a diesel. Didn't some of them have a tank pump AND a lift pump on the frame? I know the old Ford's did, not so sure about the chebbys

 

[Schurkey]

1991 Chevy c1500 short bed 7.4 with a 25 gallon tank.

Sorry just happened to re-read post, I was talking about a gasser, doubt it's same steps for a diesel.

What diesel?

 

[Ehall8702]

What diesel?

Yep ,man I gotta quit multi-tasking! My brain saw 7.3 ( yeah that's a Ford diesel I know),I thought diesel and just spun into stupidity I guess. My first statement stands then lmao. Sorry