Still no Start

sdw

Registered User
My '91 still won't start.

What is happenning is:

When cranking the injectors are pulsing at roughly 2,500 rpm. The spark is pulsing normally.

I went through the no start list and the only thing I found was a short in the cam wiring.

Any thoughts on why the injectors are pulsing at hyper speed flooding the engine?

I am running a QH with extensive mods.

Sean
 

David Neibert

SCCoA Admin
Are you sure that QH didn't lose the tune ? Battery died on my QH and it lost the tune, fouled all the plugs just trying to start it a couple times. Had to use my back up chip and at least three new plugs before it would even try to start.
 

sdw

Registered User
I took videos of the injector pulsing and it pulses at roughly 2500. I will replace the battery in the QH and reload the tune, easy to do as the EEC is not installed into it's holder.

I'm pretty sure the fan does not come on high when the key is in the on position. Is that indictive of a QH failure?

The car is in my rental garage across town so I can't get to it till next week to test.

Thanks for the suggestions
 

Tim Groth

SCCoA Member
I took videos of the injector pulsing and it pulses at roughly 2500. I will replace the battery in the QH and reload the tune, easy to do as the EEC is not installed into it's holder.

I'm pretty sure the fan does not come on high when the key is in the on position. Is that indictive of a QH failure?

The car is in my rental garage across town so I can't get to it till next week to test.

Thanks for the suggestions

Prior to the no start issue did you have prior issues? My QH chip failed a few months ago for the 2nd time so its pretty fresh in my head.

-Tim
 

ALS35

SCCoA Member
My quarter horse failure acted the same. My test was to simply remove it a try to start. It should start but run like crap because the stock tune will not know what to do with your mods.
 

sdw

Registered User
Thanks to David pointing me at the plugs. They were certainly fouled from the rich condition.

When I pulled the QH the negative connection on the battery holder was broken. I don't know when that happened but I hope it was when my car stopped running.

i've got new plugs and am going to install them and the new plugs and keeping my fingers crossed I will have a car that runs again!

Sean
 

sdw

Registered User
Still no start. Did have an almost hiccup which hasn’t happened before.

urgh.
 

sdw

Registered User
Still working on this. : (

I’m sure the injectors should pulse with the spark. In my case the injectors pulse very quickly while the spark is firing “normally”.

All of my investigation and troubleshooting has only ever revealed a short in the cam sensor harness.

I got a replacement computer but didn’t find the short until the replacement was installed.

Now I wonder whether both my computers have ended up fubar’d given how quickly the injectors are pulsing.

I thought that if I floored the gas pedal that would stop the injectors from firing. But that did not happen, they still pulsed very quickly.

Any thoughts?
 

KMT

Registered User
But that did not happen, they still pulsed very quickly

When I've had this happen on my SC, it was usually from something in the cabin restricting the gas pedal. If holding down on the pedal with your foot is how you test injector shutoff, you might want to go under the hood and manually move the linkage open to full stop, while having someone turn the key to try starting, or, if you have a button test lead, jumper at the solenoid near the battery, key on.

How are you testing injector pulse? Noid lights?
 

sdw

Registered User
When I've had this happen on my SC, it was usually from something in the cabin restricting the gas pedal. If holding down on the pedal with your foot is how you test injector shutoff, you might want to go under the hood and manually move the linkage open to full stop, while having someone turn the key to try starting, or, if you have a button test lead, jumper at the solenoid near the battery, key on.

How are you testing injector pulse? Noid lights?
Testing with a noid light, yes.

I think I should be able to manually open the throttle linkage and crank. Will test that and see what happens.

sean
 

sdw

Registered User
Testing with a noid light, yes.

I think I should be able to manually open the throttle linkage and crank. Will test that and see what happens.

sean
Manually opened the throttle to max still was pulsing the injectors.

Is that a function of the TPS or is there another sensor that is supposed to shut that off?
 

KMT

Registered User
I assume the ECU makes the call, based on feedback from the TPS.

Sorry if I missed it, aren't you on ECU #3 now? When swapping ECUs, do you tighten the center bolt on the connector, eacb time?
 

sdw

Registered User
I looked up troubleshooting the TPS and will do that next time I am at the garage.

I am only on ECU 2, lol.

But as I said i did not find the short in the cam sensor wiring until after I had installed ECU #2 so if the short took out #1 it may have done that with #2.

So I will check out the TPS and if that is ok I will get another ECU to try.

Sean
 

DOUG H

SCCoA Member
You could also check the return signal voltage from the TPS at the ecu connector to verify
the sensor & harness are transmitting WOT signal. 0.7V at closed & 5.0V at full, if my memory
is correct. You should double check in your manual for your year though to be sure.
 

KMT

Registered User
About TPS voltages...they don't have to be specific values so much, as long as the range is 4.3v
 

sdw

Registered User
I am hoping to find the TPS totally out of whack!

Thanks for all the feedback.
 
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