'98 W/ TBI got new fuel pump, ran for a day and croaked (done did the searches)

Hello all,
Ive been scouring this post for a couple of days, It looks like a good one so I hope ya'll can help.

My friend has a 98 blazer V6 with the TBI that was stalling intermitantly then finaly died.
We knew the fuel pump was going south because it sounded like someone was making margharitas in the gas tank.

We had it towed to my driveway and I put a new pump in.
I did the MU112/MU86 rebuild kit isntead of the whole MU because the vane pump and hoses are only $60 as opposed to $300 or so.
Long story short, it started fine and ran fine untill the next afternoon when it died on the road.

So I figured with new pump, all of the old crud in the lines clogged the filter.
So Last night I changed the fuel filter in the Safeway parking lot.

Still no start.
Now I do my own work on my Ford Powerstroke and classic Volvo's which are a different beast from this truck, but heres what I tried/found.

Fuel pump egnages momenteraly with ignition is on, like its supposed to.
Opening the schrader valve on the fuel rail and jumpering the FP relay gets a good spray of gas coming from it. (I know this is not a good a test as getting a fuel pressure reading, but I dont have a tester)

Oil was low, so topped that off in case the oil switch was cutting out the fuel pump, no change.

Jumpered the FP relay and cranked the engine to see if the ECU was keeping it from coming on, but still no start.

All fuses in the fuse center and under the dash tested good

She gets a good, big, orange spark from both the coil and from plug #4 when cranking, so that tells me the CPS,Coil,and Distributer are good.

Pulled the air plenum off the throttle body and cranked it, in case the air filter was clogged or blocked, no dice.

I can rear the fuel regulater or something making that soft buzz under the hood which I think is normal.

So as far as I know I got spark, fuel & air going to the throttle body, but cant tell whats going on from there.
The "Service Engine Soon" light is on, but I didnt catch any obd codes on the carchip.

So, anyone got any ideas?
I'm about to tell her she needs to get the thing towed to a mechanic who knows what thier doing, but that costs money that she doesnt have. So I want to make sure I havent overlooked anything dumb.

Thanks for your input.
Dave.

If the light is on there is a code set. If the carchip isn't reading it then I suggest you try a normal scanner. Autozone has them in their loan-a-tool program. They are about $200, but they give your money back when you return it.

If the codes don't reveal anything that would cause a no start, you need to check the fuel pressure with a gauge. These engines are very tempermental when it comes to fuel pressure, low fuel pressure is the number one cause of no starts.


When you turn the key on, the pump runs for 2 seconds, while it is running the pressure should be 60 - 66 psi

After the pump shuts off, the pressure should hold steady between 55 - 60 psi.

BTW the engine isn't a TBI, that is just an air intake, there are 6 injectors inside the plenum.

Thanks Blazee, I'll keep that in mind.
Probably not a tbi then, I was kinda matching the pictures in the Haynes manual to what I was seeing under the hood. :S

I probably mispoke then when I said I pulled the air plenum from the throttle body then.
What I did was pull the big, plastic tube that goes from the air cleaner to the air intake on the TB- er thingy.

Apparantly the carchip will only catch the obd code if it happens when it is plugged in and wont read it from the memory :P
I'm going to pick up a code reader after work and see what it says.

Can a regular air gauge be used to test the fuel preasure if I only plan on using it once?

I would borrow a fuel pressure gauge from the local Autozone.

Also, good spark is not orange, it should be blue.

hi I think that I have the same problem as volvophile. If I check the psi and it is not around 60psi do I need a new furel pump or is it poss that a relay is bad.
Thank you