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98 Turns over but no start

Bob M
09-12-2007, 12:43 AM
Let me start by apologizing. I fired off a quick email to a forum member as I was running out the door to catch a cab after my 1998 Blazer 4WD wouldn't start. He was gracious enough to reply (thank you thank you) but as I sit here in the hotel going through old posts I realize it defeats the purpose of the forum to go off line one on one. Everyone should benefit from my troubles (stupidity)...hope that makes sense. Here we go,

Hi, my name is Bob. I am kinda behind the eight ball right now and was hoping you could help me. I have a 98 blazer 4wd. I has been running good except for a few weeks now, the airbag light has come on intermittantly. Ran fine when I parked it. Next morning, it cranks and cranks but no start!

I have seen posts about fuel pumps and wiring harnesses and need to come up with a logical approach.

1. I have never heard my fuel pump but will crawl under and have a listen.
2. It's been years since a tuneup so first order is to replace cap, rotor, plugs etc.
3. Sounds like there is a wire somewhere that I can check voltage and/or power up to test fuel pump. Will find and do so. Ideas where to look for it?
4. Verify spark...pull a wire and look? Is there a better way?
5. See if it will run off of starting fluid. (a pseudo spark test I guess)
6. Check fuel pump relay by swapping with another of same number? True?
7. Fuel pump pressure if running...where is the best place to do this?

I will return home Friday and jump on this as I am vehicle-less until I solve this. Please weigh in and help me focus my diagnosis.


09-12-2007, 08:00 AM
You have it about right. First check for spark and then for fuel. Once you find out what is missing then check systems from there.

09-12-2007, 01:10 PM
When you turn the key to ON (no need to turn all the way to START), you should be able to hear the pump prime (open your door) for 2 seconds, at which time the relay kicks off the pump prime circuit. If you can't hear anything (other than perhaps the relay click off in your glovebox), then your pump is a likely culprit.

I just went through this with our 97 and spent a lot of time checking the wiring and relays to avoid having to replace the pump. I couldn't identify any other causes, so invested in a Delphi/GM pump installation and that took care of it. Also, if you decide you need a pump, I have an extra new Delphi pump that I can make you a bargain deal on if the 98 is the same as a 97 4-door (may not be). My local dealer wanted $572 plus tax for just the pump as I recall, internet $300+. The advice around here is to avoid aftermarket pumps.

09-12-2007, 04:43 PM
A quick shot of starting fluid will determine if the problem is due to a lack of fuel. The fuel pump relay on 1998 is located in the underhood fuse box, (driver side inner fender next to the air filter housing). Inside the fuse box cover is a diagram of fuse and relay placement. Locate the fuel pump relay, 1/4" in front of it is a recessed open terminal, that terminal is connected to the grey wire that feeds the fuel pump. Using a voltmeter or test light will tell you if the circuit is getting power for 2 seconds after the key is turned to the RUN position. If it does, the PCM is able control the fuel pump circuit, and the relay is good. A fused jumper wire from battery positive to that terminal will energize the circuit for testing purposes all the way to the fuel pump.

At 100,000 miles, a tune up should include A/C plugs #41-932, distributor cap, rotor, wires, air filter and fuel filter. There's a whole list of other items due at that mileage, but to keep the engine running reasonably well, that should be a good place to begin.

Here is a guide for checking fuel pressure:

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump through a relay continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM/VCM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port in the steel fuel line near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates excessive leak down. Possible places to leak are the fuel pressure regulator, the fuel lines under the upper intake manifold, a fuel injector that is stuck open, a leaking fuel line or connector, or the check valve in the fuel pump assembly.

Here is a link to an inexpensive, and adequate fuel pressure tester: Accurate diagnosis of an internal fuel leak requires additional test equipment. In some cases it requires the removal of the upper intake manifold.

Hope this helps.

Bob M
09-12-2007, 06:02 PM
Thank you to all that have jumped in to help. I will fly home tomorrow and get started. Great lead on the fuel gauge! I'll get it straight away.

I think I'm all set to start trouble shooting. Of course I'll let everyone know my progress. One last thought before I get started; some posts have refered to a pickup coil. Is this something to change out of hand and/or how is it diagnosed.

Thanks again, I'll update you Friday night.


09-12-2007, 08:36 PM
The pick up coil is inside the distributor on older style ignition systems. It sends a pulse signal to the ignition module which in turn fires the ignition coil. Your 98 is not equipped with that style of ignition system.

Bob M
09-14-2007, 08:26 AM
Here's the latest...

I got home yesterday and turned on the key. The fuel pump screeched! It never make a noise before. The truck then started right up. The pump continues to whine very loud. Absent any further diagnosis, I am calling this pump trashed!

I got the tank drained and off. I broke the forward strap bolt and fought the fuel "not so" quick disconnects on the top of the tank but finally won. The metal fitting on top is a rust pile. I finally got it off. I am off to the dealer today with my shopping list.

Fuel Pump
Tank Strap Bolt

More to come!


09-14-2007, 05:33 PM
Better be wearing a diaper when you go to the dealer parts department. Definitely worth shopping around. There are several online companies that sell Delco pumps for a couple of hundred dollars less than the dealer.

09-14-2007, 06:55 PM
Better be wearing a diaper when you go to the dealer parts department. :lol: For sure, look around.

Bob M
09-14-2007, 07:02 PM
OK, here's the scoop. I went on the cheap and bought an after market through PepBoys. Chevy wanted $439 and I got mine for $280. Should have spent the money. The truck is running and seems to run good, but boy what a horrible day to get there.

The pump was enough different to not fit down into the recess enough for the locking ring to work. The new locking ring I bought this morning was identical to the original except for the rust. But the aftermarket pump had a larger diameter top and caused me to take the ring to a machine shop and have it cut bigger. Then I realized the detent tap to align the pump was different and if installed using it as guide, the 3 fuel nipples were oriented such that you couldn't connect them. I cut the detent tab off and it all finally went togther.

Lessons learned. 1) Ask lots of questions before taking on a job like this. It sure helped me. 2) Listen to the advice you get! 3)Stick with OEM. After the extra time and money I am no better off than if I spent the $439. 4) Buy penetrating oil by the gallon and start soaking nuts and bolts days before you do the job!

Thanks to all who helped me through this. Good advice from everyone. A special thanks to Dino55!!

Hope I can return the help sometime....


09-14-2007, 07:54 PM
Going through all that screwing around... I'd say they gave you the wrong pump. You're much more patient than most people. If that happened to me, pep boys would be wearing the lock ring for a neckalce and the pump would be... let's not go there. Anyway, glad you got her going.

09-15-2007, 06:24 AM
Going through all that screwing around... I'd say they gave you the wrong pump. You're much more patient than most people. If that happened to me, pep boys would be wearing the lock ring for a neckalce and the pump would be... let's not go there. Anyway, glad you got her going.

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
I agree with old master.................

Glad your truck is back on the road again Bob....................

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