I was running down the list of trouble shooting of why my car (81 turbo)briefly starts then stalls (flooding out) when I came across a piece of wiring I do not understand.

Using the service manual for 81 turbo

on EF 26 in regards to testing the CHTS, measure resistance at pin 23 to ground and it should be over 2.1Kohm. So doing this I got infinity, ok bad sensor or harness.

Upon replacing both, still infinity on the meter. Does not make sense so I looked on the wiring diagram (below) and found the other wire runs to pin 26. Measure between 23 and 26 and I get 3.9Kohm, which is correct off the table for 50 F for the CHTS.

pin numbers for connector on diagram:

29 30 31 32 33 x 35 36
21 22 23 24 25 26 27 28

Now I say to myself that I have a grounding problem since pin 23 to ground is infinite. Since the diagram does not show the CHTS being directly grounded I followed the 26 line to see what else it is connected to.

line 26 is connected to the AFM. On the diagram it shows grounding of AFM at least at the case. So now I am thinking that ground through the AFM to line 26 is the problem, so pull out the manual EF-61,EF-62 to test AFM.

It states check insulation resistances between body and pins 26, 31 and 33 and it should be infinte for all. Which it is. So 26 can not be grounded through the AFM chassis.

So going back to the beginning, with out any grounding how can you get a resistance reading from pin 23 to ground? Is the manual wrong? Does ground come through the CPU via the connector?

Here are some other values from the AFM:

33-26 200ohm
33-31 120 flap closed, 480 ohm open
26-31 160 ohm closed, varies from 90-340 ohm when flap is moved by not linear.

I guess my though is that if resistance goes to infinite for the CHTS and AFM then the CPU would think the engine is cold and the flap is wide open causing it to making the injectors flood the system. Why I think this is that when I first go to start it, it hits, revs up then stalls. Then next cranking it hits one cylinder once or twice, third or fourth crank has nothing but a serious gas smell.

Other stuff: new plugs, cap rotor, wires and coil. set timing.

Thanks for any input!

 

have you checked your fuel pressure? often people go out looking for real exotic reasons when it is something simple and obvious. check the chts at the chts. check wiring continuity back to the ecu. some other obvious things that people ignore

Get your battery load tested (better yet buy an Interstate battery and be done with battery woes for better than 5 years). Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion.

 

Thanks for the reply.

I just got the fuel pressure gauge today that I will install inline and leave.

Other things to add: New premium battery, cleaned up terminal connectors and any grounds I could find, ground runs from battery to body to starter, new connector to CHTS, new CHTS, CHTS resistance is right (just not as discribed in manual(pin 23 to ground) and AFM checks through harness.

 

the only premium battery there is an Interstate. had one in my 88 E150 for nine years still working when I sold it. 6 years in my s130, 6 years in my Ranger, 7 years in my z32TT. never had a problem as long as i didn't leave the dome light on. only got 3 years on my 86T but again never a problem

 

I"be had four Interstates fail on me. One was a full warranty replacement and the other three I had to fork out for. There are only a few places that make batteries and slap various labels on them.

Try ringing out from one end of the cable to the other without the AFM connected