blmcquig

iTrader: (15)

hey ive got a no start problem, so i went back through some old threads and found a few tests to do on the ecu, and id like you to give me your expert opinion. also, anyone else who has any good advice is welcome to chime in.
now, the car is an 87 turbo shell, with an NA engine, however it is out of a vert from 88. high impedence injectors, no resistor pack, so dont suggest that (already had 4,050,382 people tell me to check it!!) anywho, on to the numbers that i found interesting:

water thermo sensor=2.229 ohms
pressure sensor= 3.489 ohms

i know its not much, but everything else checked out okay, and the car STILL wont start! does anyone think these could attribute to this condition?? thanks for the help in advance!

HAILERS

The water thermo sensor sounds about right for a cold car.

The pressure sensor should not be ohm'd out. You should check for DCVOLTS with all the plugs connected up and key to ON. You can unbolt the pressure sensor and flip it over where you can see the elect plug. Put the meter neg lead on a known gnd (like the bracket that hold the pressure sensor to the body) and then backprobe the brown/red wire with the meter on dcvolts. It should read 3.5 to 4.0 vdc with the key to ON.

Do you have a spare cas out of another engine? Take it and connect it to the cas elec plug that is now on the cas in the engine. Key to ON. Spin the spare cas's bottom gear with your fingers and listen for clicking/snapping indicating the sparkplugs are firing. Lay a plug wire on the fender if needed so you can see the spark. You do not have to spin the engine over to do this. It saves wear and tear on the starter and engine since your just interested in if the plugs are firing.

IF the plugs are firing, then now disable the two coil assy by pulling their plugs off. Now spin the cas gear again with key to ON. Listen for the primary injectors clicking. You should be able to hear them click when the cas bottom gear is spun.

IF the spark is there and the injectors are clicking...........................got me why it won't start unless the timing is waaaaaay off or the engine is bad.

Before doing the above, make sure the ENGINE fuse is good in the interior fuse panel.

I'm not sure what harness your using on the engine. The non turbo? or turbo. AND the rest of the harness's in the chassis are turbo???????? IF the rest of the harness's in the chassis are turbo, I'd use the turbo harness on the engine.....because there are a number of wires in the Front harness that won't mate with the non turbo EM harness on the engine. The plugs will mate but some of the wire functions are different.

And last of all.......during START the ECU looks at rpm, a signal on pin 3D showing the key has been put to START and it looks at water thermo temperature. A car should start if the afm plug is off or the pressure sensor connector is off. It just won't run more than a couple of seconds because after the rpms get over 500 rpm THEN the ECU uses the afm for fuel.

HAILERS

But also do this. PUll the small plug off the ECU. Key to ON. Meter neg lead to a good gnd like the bracket that holds the ECU on the chassis. Probe the injector wires in the harness plug. Light green, light green/black, light green/red, light green/white. All should have battery voltage with the key to ON.

You might make that one of the first things you do. That voltage shows the injectors are getting ...voltage. No voltage means your problem is......no voltage to the injectors so they ain't a gonna fire/operate.

imloggedin

good info!

nu-rx7junkie

iTrader: (1)

Actually check the injectors. They can pulse and click and no fuel come out. Mine did it. Take the fuel rail with injectors loose from the manifold. Hold the injectors firmly in the rail with your hands, have a friend jump the fuel check connector on the right fender behinf the AFM , then jumper the fuel injectors to ground and a quick tap on positive fuel should squirt out . (mine did not) i cleaned them with throttle body cleaner and lightly pressed the plunger tip with a pen to feel it move. them tried firing them again and they worked. And my car ran after that.
My 2 cents

blmcquig

iTrader: (15)

ahh, my bad, i meant:

water thermo sensor=2.229 volts
pressure sensor= 3.489 volts

volts, not ohms.
everything else checked out that you said to do (CAS trick included)
ive also checked the timing as according to someones website, and my running TII.

blmcquig

iTrader: (15)

wonder if i get another pressure sensor if thatll make a difference....