Working on an 86 S10 Blazer 2.8L 6cyl 4X4. Will crank over but won't start. Also noticed the radio backlighting, dome lights and horn suddenly did not work. Replaced the ECM unit (hasty decision-I know, but with the multiple sudden failures, made sense at the time.) Ran a diagnostics on him,but there are no codes...it's an '86. Tested the fuel pump and lines with a voltmeter. Now replaced, but still will not start. Has a new Optima battery and cranks over strong. Used some starter fluid to get it to start, but will not stay running. Am now looking for the FPR and will try replacing that, AND re-wiring the electrical lines connected to the entire fuel pump system. Perhaps an electrical short somewhere? OR any ideas ? I am no novice to auto repair or diagnostics but this is really boggling my mind. Sure would welcome any insight, tips or shade tree hints for zeroing-in on this multifaceted problem. Gotta get my little autobot up and crawling again. Thank you in advance... Dzr

 

Is this engine TBi or carb?

 

86 was first year of TBI.


What are you using to test for voltage?

 

Check the ECM B fuse in the fuse panel by the left drivers foot.

 

Will check that. Thanks Already replaced the entire ECM, though. Think I got it narrowed down to the oil pressure sensor and sending unit near the oil filter. Appearantly these fail often and are easily overlooked. The connector has melted and the wiring is exposed. The trouble I am having now, however, is: I find where three (unexposed) of the four wires connect, the exposed wire with the female end has a diode in it and does not seem to have an obvious male counterpoint to plug into/onto. Any idea?

 

Yes it is TBI. Testing with a voltmeter.

 

SO! replaced oil pressure/sender unit (3 prong) was DEFINATELY bad, now more fuel cucuitry is activating...(fuel relay, tbi, ecm, ecmb) HOWEVER: now the parking lights are refusing to turn off( unless of course the main batt is disconn) and fuel pump still not sending fuel at very much pressure at all. the TBI did drip a little tho. the rear lead for the fuel pump is now reading zero volts and the park lights WONT TURN OFF!!!!!! wtc...anybody??? please?

 

Sounds like you might have some crossed wires. For the parking lights, pull fuses til you find which fuse its on to trace the wires that way. Also, on Autozone.com there is wiring diagrams that could help you if you don't have diagrams already.

Use this link hopefully: | Repair Guides | Wiring Diagrams | Wiring Diagrams | AutoZone.com

Also, there should be a wire harness (1 wire) on the firewall. From the air cleaner look directly back to the firewall and a little left. There should be some wires there and one of them is just a plug. Jump this wire with 12V + and it should turn your fuel pump on. You can do that to test the fuel pump. I could get a picture of this wire on my truck if u need.

 

I too am experiencing similar problems. 1989 s10 blazer, 4.3, 4x4. Was driving down the road when it shut of. Would turn over, but would not start. Towed it home. Started troubleshooting the next day. Noticed I did not hear the familiar hum of the fuel pump when first turning the key. Suspected fuel pump as well... but...

Parking lights and turn signals work. Headlights do not.

Dome light and glove box light do not work, but map lights on rearview mirror do.

No dash lights.

Horn does not work.

Power locks and power windows work.

Push button release for back hatch does not work. This actually happened right before the fateful voyage. I used the key to unlock the hatch, loaded up, and took off. Have not yet determined if this is relevant.

Radio will not display time or tune a station, but will produce static when turned on.

Blower fan for heat/defrost will work on lower settings, but will shut off when turned to highest setting.

Replaced fuel pump relay and fuel pump/sending unit.
Checked all fuses in fuse box under dash.
Checked for error codes. Not showing any.

Not that it matters, but I replaced the gas tank when I replaced the fuel pump/sending unit to avoid having to do it later on down the road. It was original and in bad shape, and I'll be in no hurry to drop that tank and mess with those connections again.

At the electrical connector leading to the gas tank, I have power to the fuel gauge, but not to the fuel pump. It also appears that where the ground wire from the tank is attached to the frame, that location is not producing a ground even after wire brushing the frame, bolt, and eyelet at the end of the wire. I can get the fuel pump to pump fuel if I attach a 12 volt power source to the hot wire and a seperate ground going directly to the negative terminal of the battery. I still was not able to get the engine to fire with it hooked up this way, but that could be due to engine flooding in the time it took me to make the connection, crawl out from under the vehicle, get inside, and turn the key.

I will keep an eye on suggestions here and follow your progress, and post things that did and did not work as I keep trying to resolve this issue. I have been at it for 4 weeks, working outside in frigid temperatures. Hope one of us has a breakthrough soon that might help both of us out. Best of luck.

 

Both of you might want to check the ground connection to the frame coming off the battery. Make sure the connection is clean at poth points and the wire is not corroded.