1990 Burb need help with engine miss

[bowstryder]

I have a 1990 v1500 with a reman 290 hp goodwrench engine. New TBI unit with 60lb injectors. All the rebuilt stuff has about 40k miles on it and the tbi has about 3000 miles on it. The engine gets a real bad miss under load and will occaisionally stall out after it miss and I let it crawl to a stop. Everything was fine until recently I noticed the fuel pump staying on for a couple seconds after I shut it down..... no problems with running. Then she started missing under a load and now the above issues have surfaced. I am going to swap out the plugs and a fuel filter (mainly because it's getting close to that time) and check in the dist. for some issues but it almost seems like a fueling issue.
Haven't gotten any codes to show up on the obd1 either. Anyone run into this or have a good idea, advice welcomed.
Thanks
Adam

 

[UK4X4]

I think your heading in the right direction, low or restricted fuel flow, bleeding the rails dry under load not enough fuel getting through.

filter -pump -crimped or rusty fuel lines- suction on the tank ...

 

[1stDeuce]

Hmm. Fuel pump runs AFTER you shut it off?? Pretty sure that's not supposed to happen... Try swapping the fuel pump relay for the horn relay, or some other relay. You might just be having problems with the relay sticking, or not contacting well, which would lead to issues like you're seeing. Your throttle body only uses about 14psi, so if the pump is running, and isn't REALLY loud, it should be making pressure, but your dying out under load really sounds like a lack of pressure allowing vapor lock... If your pump is marginal, putting the engine under load (using more fuel) is causing the pressure to fall off and that would lead to the problem you're seeing. You might also check the soft fuel lines to make sure they're not kinked anywhere. On a truck that old, it could happen over time if one of the soft lines was a little long. Change the filter too, it'll be fun. It's probably not plugs.
Seeing nothing else, if you haven't put a fuel pump in it lately, it's time. Have fun!!

 

[bowstryder]

Ill check the wiring when I tear into it. I should have mentioned that the tank and pump are only a year old with about 4k miles of trouble free fun. As far as the other tune up items, I just threw that in there as it's about time for that.

 

[Larry]

Hmm. Fuel pump runs AFTER you shut it off?? Pretty sure that's not supposed to happen... Try swapping the fuel pump relay for the horn relay, or some other relay. You might just be having problems with the relay sticking, or not contacting well, which would lead to issues like you're seeing. Your throttle body only uses about 14psi, so if the pump is running, and isn't REALLY loud, it should be making pressure, but your dying out under load really sounds like a lack of pressure allowing vapor lock... If your pump is marginal, putting the engine under load (using more fuel) is causing the pressure to fall off and that would lead to the problem you're seeing. You might also check the soft fuel lines to make sure they're not kinked anywhere. On a truck that old, it could happen over time if one of the soft lines was a little long. Change the filter too, it'll be fun. It's probably not plugs.
Seeing nothing else, if you haven't put a fuel pump in it lately, it's time. Have fun!!

x2 :iagree:

 

[cyclic]

You need to check the pressure and check the relay. Both are probably bad. The relay is easy, figuring out where the pressure loss will be a little harder.

 

[bowstryder]

Folks, I greatly appreciate the input. I will give the aforementioned advice a shot when I get the time this weekend. Thanks again, and I'll keep you posted as to what I find.

 

[clandr1]

You need to check the pressure and check the relay. Both are probably bad. The relay is easy, figuring out where the pressure loss will be a little harder.

Where is the relay? My fuel pump also stays on for a few seconds after I shut off the key. I thought it was normal, but apparently it's not.