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I am having trouble after tuning up my 1990 gmc jimmy. I added an aftermarket fuel pump (just added it in line not in the tank) then added new plugs, wires, rotor, and dist cap, but after starting engine, it surges for a moment and when you accelerate fast it acts as though its starving for fuel or just chocking down. It seems to run smooth at start up and Ive checked the firing order several times and it seems to be correct.

posted by  mobo96

does the pump in the tank no longer work if not the inline pump will be fighting the intank pump trying to suck fuel throught it
check the attachments for the firing order

posted by  osborste

Thanks for the advice. I kinda thought that might be an issue with this vehicle, but was not sure. I did this same thing on an earlier truck without any problem, but it had a manual fuel pump and I added an electric. As far as the firing order, I have that correct and it is a 5.7 liter, I was just needing to know if there were any electronic firing mechanisms that needed to be checked or maybe vacuums that needed to be checked. Thanks for the input. Also, I disconnected the intank fuel pump, but it is still in the tank, I guess you are suggesting it be totally removed? Is there a way to bypass it without all the trouble of removing the tank ?

posted by  mobo96

so its a fullsize jimmy
the fuel tank needs to be taken down then when you have the pump/float assembly out measure the lenght of the pump and add that to the pipe with another pipe useing the rubber hose joiner to join it back together

posted by  osborste

I tried what ya said and that made no diffrence at all, same problem. I removed the entire fuel assembly and replaced the pump with a peice of fuel line, but it made no diffrence. When I push hard on the accelerator, it just coughs and sputters. This must be electrical and not fuel related. Anyone got any suggestions?

posted by  mobo96

how much fuel presure are u getting need 9 to 13 psi
your fuel pump might not be pushing enough (plugged fuel filter)
is the pump before the filter or after
tank-pump-filter-engine

posted by  osborste

The pump is after the tank and there is no longer a filter in line, I removed it. I also removed the pre filter that came with the pump as it leaked a little. I havent checked the fuel pressure and I have no way of doing this, I guess its time to take it to the shop.This sure seems like a ignition or elec problem to me.

posted by  mobo96

you took the filter out nooooooo!!! all the small crap in the tank and from the gas stations holding tanks just plugged up your injector's

posted by  osborste

I guess you didnt understand that the problem began long before I removed the filter and that the tank is spotless and the injectors are working flawlessly. It is not multi port, just throttle body injection and all is well with that. Im taking it to a shop for computer diagnostics tomorrow, this is getting to be too much for me , and I have put it up for sale and cant let anyone drive it in this condition. This has got to be elec or ignition, but Ill post the results after I get the news from the shop. I appreciate your trying to help, but its in Gods and the mechanics hands for now, ha ha .

posted by  mobo96

you should still have a filter(prevention)
ya i knew it was throttle body injection there's 2 injectors
good luck

posted by  osborste

shoulda just done it right in the first place and you cheaped out not once not twice but numerous times, why didn't you just put a new fuel pump in it, oh thats right everyone knows more than the guys that designed your truck :thumbs: good work douche i hate people like you......and there are many of them, i hope the shop rapes you for many many dollars cuz they will have a bitch of a time fixing what you ****ed up, your pro...die

posted by  BanffAutoSpa_ap

...sounds like someone's cheerios got peed in this morning... :hi:

posted by  dodger65

Yeah, that's a bit extreme. I mean, sure, the kid ****ed up, but I'll bet pretty serious cash that we all did shit like this when we were learning. I'll admit that I did in my day. At least he's coming to us with all the pertinent info.. much better than most of the people who post problems.

mobo96 - I know you said you checked the firing order, what about the timing? It could be off, that'll cause exactly the problem you're having from the sounds of it.

I guess since it's in the shop, we'll know shortly, but I've seen 350's with that problem. Has it been backfiring, or just weak?

And never run the engine without a fuel filter. If you think it's clogging up and causing you trouble, just replace it, but you're risking some serious damage to the engine going without one.

posted by  Martian

Well, well, seems like my little problem brough out the worst in a wanna be mechanic(banffautosp). Dont know what I did to deserve that, but I appreciate all the other positive comments (martian, osborste etc) and by the way, it was the lack of fuel pressure from an after market fuel pump, which was sold to me from a bonified autoparts man that said the book called for that model. He said either one would work as the pressure was the same.The only reason to choose the inline instead of the in tank model, was lack of tools on my part. I truly believe in keeping oem when possible, but seeing as Im disabled and dont have the money to throw into a vehicle, I do as most men do, I improvise.I am a novice compared to most of you Im sure, but the shop had tools I didnt and whether or not Mr. sourpuss knows it or not, I had enough sense to let a pro troubleshoot it and then I repaired it, so all's well that ends well. I enjoyed and appreciate all the help from the forum, but watch out for that guy with the attitude problem, hope he's not driving around where I live.

posted by  mobo96

the parts store computers pop up that universal fuel pump p/n for almost every car. i think the pressure might be that same, but only for a carb'ed application. i think it prob. lacks the volume for a fi app. maybe if you tried pinching off the return line, it would have run. i guess the world may never know...

:laughing: ...life is good when you're a monday morning quarterback... :laughing:

posted by  dodger65

Thanks dodger, youre probably right, but its all over now and shes up for sale. Its been a great truck and I hate to sell it , but I gotta eat. Thanks to all who tried to help.

posted by  mobo96

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