94 Jimmy hesitates and dies on acceleration

[John Hart]

Hi,
I have a 1994 Jimmy that, up until recently, has performed great.

Then one day, the fuel pump died and I had it replaced.

About a week later, I was driving down the highway, and it started to lose power. Over a 10 mile stretch, it got worse and worse, and I barely made it home.

The following day, it started up just fine and I drove it to work, but I noticed that it started to lose power again toward the end of the trip. Same thing coming home.

So over the past week or so, it has gotten progressively worse. It starts fine, idles fine, and has plenty of power for about 10 minutes...then starts dying out on acceleration.

I've replaced the fuel filter, plugs, distributor cap and rotor, EGR, MAP sensor, Ignition control module, plug wires, and coil.

I can't figure out why it runs so well for a little while, then starts to die out.

Any ideas?

 

[Molson02536]

Hi,
I have a 1994 Jimmy that, up until recently, has performed great.

Then one day, the fuel pump died and I had it replaced.

About a week later, I was driving down the highway, and it started to lose power. Over a 10 mile stretch, it got worse and worse, and I barely made it home.

The following day, it started up just fine and I drove it to work, but I noticed that it started to lose power again toward the end of the trip. Same thing coming home.

So over the past week or so, it has gotten progressively worse. It starts fine, idles fine, and has plenty of power for about 10 minutes...then starts dying out on acceleration.

I've replaced the fuel filter, plugs, distributor cap and rotor, EGR, MAP sensor, Ignition control module, plug wires, and coil.

I can't figure out why it runs so well for a little while, then starts to die out.

Any ideas?

Was the wire harness from the sending unit to the frame replaced??? From what you have described, it sounds like you have a ground issue or a wiring issue. When the wires heat up from the electrical current and if there is a break in it.

The current flow may be broken and causing a low voltage to the sending unit. Start with inspecting the wire harness and the ground wire to the frame also which is separate from the harness.

It would not also hurt for you to replace the fuel pump relay which is located on the fire wall just to right (Passenger side) of the brake booster.

Good luck and keep us posted.

 

[John Hart]

Thanks...I'll give that a try tomorrow. I was about ready to pull the fuel pump and take it back to the store. I'll give the wiring a good going over before I do that.

many thanks.

 

[Molson02536]

Thanks...I'll give that a try tomorrow. I was about ready to pull the fuel pump and take it back to the store. I'll give the wiring a good going over before I do that.

many thanks.

NO worries, surprised they did not sell you the wire harness. It's about $15.00 and worth more then that if you have the old after you put everything back to together.

Keep us posted and check your fuel pressure during your cold starts and when your engine starts acting up. You need 62-65 PSI to start and then should drop about 5 psi when the engine is running. At 55 PSI your going to have issues, good luck and be safe.

 

[John Hart]

Ok....I decided that I wanted a professional to check out the fuel pump and wire harness.....Mainly because it was too cold outside and I had other work to do.

It took a couple days, but he just got back with me and said that the ground wire going into the sending unit was bad, and when he was fiddling around with it, it just came right out of the sending unit.

Anyway, the bad ground wire also caused to burn up the armature on the new fuel pump motor. So I got to warranty the pump, and opted for a new sending unit...and all is well.

I've always heard that it isn't a good idea to replace the pump without replacing the sending unit...but just couldn't swallow the expense at the moment. I guess that'll teach me. All my easter-egging since installing the pump has cost me 3 times more than the sending unit would have cost me in the beginning.