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Rixster
Rixster, ASE Certified Technician
Category: Car
Satisfied Customers: 282
Experience:  Owner Rix Automotive & Mobile Repair 27+ Years Exp. with all makes and models cars and Lt. Trucks
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1993 GMC: 4x4..distributor..cap, rotor, wires, battery, alternator

Customer Question

I have a 1993 GMC Jimmy 4x4 that will not start when cold. Have replaced ignition coil, distributor pick-up coil, ignition module, temp. switch, map sensor, cap, rotor, wires, battery, alternator. Only thing I can think of now is the EMC. Have checked fuel system, psi 160. But will start eventually after 15 amp high boost from battery charger. Will start fine for that day, but not next. Help.
Submitted: 5 years ago.
Category: Car
Expert:  Rixster replied 5 years ago.

Hello! I'm Rixster...

I'm going to help you out on this but I need some clarification on a couple of things...

You said you checked fuel pressure?

What was the reading in PSI? should be about 9-13 PSI.

Does this only happen when cold?

Customer: replied 5 years ago.
This truck has a CMFI, 4.3 engine with the fuel rail. Test port indicates 60 psi from pump in tank. Just tested TP Sensor- .70 volts to 4.5 volts at open. EST resistance is 14000 ohms cold. Have not checked hot. Any other ideas? Thank you
Expert:  Rixster replied 5 years ago.

Okay so you have a CPFI engine and that reading is acceptable.

The Throttle Position Sensor Read is about right as well.

The Engine Coolant Temp. Sensor reading (14K ohms) tells me you are at about 0* F or lower.

Is this the case? If not it may be trying to overcompensate for a lower that true ambient temp. Are the plugs wet with fuel?

Is there good spark?

Can you get codes from the ECM?

Check these and get back to me and we'll see where we are going from there.

I don't recommend throwing an ECM at it just yet until we know for sure.

 

Thanx! -Rixster

Customer: replied 5 years ago.
We replaced Engine Coolant Temp. Sensor. Plugs were wet with fuel, so replaced those. Has good spark. Just a code 12. Counted 14 tries on starting today, didn't start. Tried 5 tries with high boost, won't catch. Anymore ideas? Thanks.
Expert:  Rixster replied 5 years ago.

It's possible the injector is faulty.

The injector for this rig is located under the intake plenum. There is one injector and six little hoses with poppet valves on them that go to the individual ports.

If you replace this make sure you place the hoses the same way as they are placed on the original one.

You can check for proper pulse with a noid light attached to the injector harness.

This is a red and blue wire harness comes out at the front left side (right side as you look at it) of the ntake plenum. Disconnect this harness, plug the light into the vehicle side of the harness and crank it. Should see an intermittent flash to show injector is getting current. If you are getting good pulse then you know your injector is stuck open or malfunctioning.

Rixster, ASE Certified Technician
Category: Car
Satisfied Customers: 282
Experience: Owner Rix Automotive & Mobile Repair 27+ Years Exp. with all makes and models cars and Lt. Trucks
Rixster and 13 other Car Specialists are ready to help you
Customer: replied 5 years ago.
Saw intermittent light with noid check. Is there anyway to check the regulator or injecter without removing plenum?
Expert:  Rixster replied 5 years ago.

No! Not that I know of.

You've basically done all the checking you really need to do. What it comes down to is

If the injector is faulty it's time to change it.

Pretty simple job. Don't forget to replace the plenum gasket too. You don't want to deal with vacuum leaks later!

Thanx! Rixster...

Customer: replied 5 years ago.

Thank you so much. New injector seems to have cured starting problem. Having you confirm my husbands thoughts helped us to spend the $$$ on the part. Will be asking questions on our 1995 GMC Jimmy problems soon. How can I request you? Thanks again Rixster. Bill and Karen(the 93 is mine)

Expert:  Rixster replied 5 years ago.

It's been fun helping. I'm glad to see all is well!

Thank you for your awesome comments. It really made my day.

You folks are awesome!

Thanx! -Rixster

Customer: replied 5 years ago.
Rixster, Truck started great at first. By next day, wouldn't start. Now have got it down to have to spray gumout into intake plenum, then starts and runs great. Moving around wires by the harness connection where checked with noid lite made it instantly die. crnak, nothing. Spray, great. Help!
Customer: replied 5 years ago.
Touching those wires seem to be occasionally. Took out and ran great. Shut it off, wont start without spray.
Expert:  Rixster replied 5 years ago.

Sounds like you may have a bad connection there. If you are careful you can extract those wires out of the connector and inspect them for tension as well as the other side for staitness.

I would'nt rule out the possibility of a PCM Failure too.

Codes???

Let Me Know!!!

Customer: replied 5 years ago.
Rixster, am working on our 1995 GMC Jimmy CMFI v6 vortex engine. After removing the plenum, drivers side has bad carbon buildup, other side looks okay. What can cause buildup on just one side of engine? Codes say multiple missfires. Has not run well for almost a year. Dealership says has carbon problem. Thanks

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