Car has spark but no injector pulse

[ncoop23]

Hello,

I can fix anything mechanical but the electrical thing... not so much. Could you help me a bit getting my car going?

I have an LQ1 that isn't starting, it has spark but no injector pulse. What could possibly cause this?

Thanks guys!

[pocket-rocket]

Check your ECM for power. Have you tried the paper clip trick to see if you can get anything from the ECM code wise? What year is your car?

[Schmieder]

I heard about this trick, but had not tried it.

Hang the injectors and rail above the block. Turn the crank by hand and watch to see if the injectors fire as the crank turns. But be SURE to disable any spark. Or else the motor may suddenly start running from hand cranking. If there is any issue then your injectors wont fire. This can help diagnosing the problem. Not sure how DOHC track the camshafts.

Or you can measure fuel rail pressure key/on and start turning the engine over while watching the pressure gauge. If your injectors aren't firing then the pressure will decay at normal rates like it was sitting still.

To get spark the CKP must be working, so rule that out.

Test the fuel injector leads for positive power with key/on. They are fired by switching a ground open/closed. When grounded, the circuit completes. It is not a power switch on/off but ground switch. Make sure the PCM has good grounds.

Check fuel pressure at the Schrader Valve.

Good luck man!

[pocket-rocket]

Not sure how DOHC track the camshafts.

The DOHC doesn't track cam position from 91-94. 95-97 do because they got cam position sensors that tracks the front intake cam.

I didn't even think of fuel pressure because I assumed it was good. See reason #1 why you don't assume in the street wise dictionary.

[Schmieder]

The DOHC doesn't track cam position from 91-94. 95-97 do because they got cam position sensors that tracks the front intake cam.

I didn't even think of fuel pressure because I assumed it was good. See reason #1 why you don't assume in the street wise dictionary.

Ha, yeah. An assumption caused me 2 months of frustration diagnosing everything possible. A simple pigtail, a lesson of assumptions.


With key on you should hear the pump priming the fuel pressure. At that point you can quick hit the schrader valve to confirm fuel is present and there is some form of pressure.

Try cycling the key on to multi-prime the fuel rails and see if that makes any difference for the better. If so, your filter may be clogged up.

Also, try 'jumping' the fuel pump relay which keeps it on 100%. If that makes a difference then the culprit is either the check valve or pump. Assuming your pump is operational.

Are all injectors failing or just some? If all are failing, I'de lean away from injector failure and agree it is either electrical or in the pump/filter region.

Also, lol. Check for fuel in the tank. Some fuel gauges get stuck. Happened to me years ago in a work van, so it does happen.