94 grand prix no start

[jydjohn5000]

hello, i am working on a friends 94 gp 3100, and i cant figure this one out... i am not getting ground to injectors, i've checked or replaced everything i can think of, cam sensor, crank sensor, computer, even changed the vats system with good one from running car just to rule it out, anyone have any clues? thank you

[CrazyHorst]

You mention VATS. I'm not familiar with that particular vehicle but I can tell you if the resistor key is wrong you can change the entire engine and it still won't start.

[Mickey#1]

If the TPS shorts out it can send too much voltage to the PCM. The PCM will then go into 'clear flood mode' & not fire the injectors. Try unplugging it & see if you get ground.

If that doesn't help then you might want to try another ignition control module.

[grandprixgtx00]

have you checked the ignition module? they are notorious on on that year 3100

[jydjohn5000]

vats is good, switched box, and resistor key between gp and monte, monte ran with gp's key and box, gp still did nothing.i switched ignition modules, no difference, i tried unplugging tps, but have not tried checking or changing it...

[Mickey#1]

How are you checking for ground to the injectors?

[grandprixgtx00]

so i assume you checked fuel pressure and are sure this is an electrical problem?

[tblake]

The ground circuit for the injectors comes from the ECM. The ECP uses the cam position sensor in conjunction with the crank position sensor(s) to determine appropriate injector pulses.

I would verify the cam is turning when the motor is being cranked.. either do a quick compression check or pull a valve cover. Becuase of a cam isnt turning, the cam position sensor wont supply a signal to the ECM.

If that looks good, find the cam and crank sensors. The cam sensor is under the intake manifolds, but I think it can be accessed by removing the power steering pump. I think your 3100 has two crank sensors, one behind the harmonic balancer and one on the rear of the engine block near the firewall. You may want to ohm these out (I dont know the appropriate values though). Also, if you go to remove the one atthe firwall, be carefull!!!!! They have been known to break off.

If all your sensors check out, I;d have to say its the ECM.

[tblake]

oops, I just re-read the initial post. So, did you change out both crank sensors?

[jydjohn5000]

tested with light, then meter, injectors have power, no ground signal, car starts up if i pour gas or starting fluid in, fuel pressure perfect. changed both cam and crank, did not change crank sensor by the firewall, was told only controlled spark timing... i did try ecm too, my buddy owns a junk yard, i was allowed to borrow one..

[tblake]

My last guess would be the one crank sensor by the firewall.....

They are a PITA! Remove the bolt, twist easy, pull out gently, back and forth, over and over again. Maybe a can of carb cleaner or something like that. Work it back and forth and in and out untill you can get that sucker out. If you break it off, the only option is to tap it through and remove the oil pan....

[tblake]

WAIT!, when you swapped ECM's, did you get one with the same part number as the one in your car? (not sure if 1994's are like this) but, did you switch the PROM chip out of the old ECM into the newer one?

[jydjohn5000]

yes changed the prom too, just tried changing other crank sensor, still nothing... im clueless now...

[severence]

Originally Posted by jydjohn5000

hello, i am working on a friends 94 gp 3100, and i cant figure this one out... i am not getting ground to injectors, i've checked or replaced everything i can think of, cam sensor, crank sensor, computer, even changed the vats system with good one from running car just to rule it out, anyone have any clues? thank you

did u try using the key?

[tblake]

Originally Posted by severence

did u try using the key?

What?