Dwell Stuck at 50% am I correct to suspect the O2 sensor?

[David T]

If you can use a scope you can read a wiring diagram. Go to D:04:06 and check the wiring to the TTS and the CSV and starter. Verify there is nothing plugged into the hot start relay plug by the fuse block. Polarity on the TTS is VERY important. Screw it up and you burn it out (and it only takes a second!). Follow this advice and it should fix the hard cold start problem. Other things to check is vacuum hose routing and pay particular attention to how the distributor vacuum solenoid is connected. If the hoses are reversed it won't work right. Then check timing. There is a good write-up in the how to's to check the vacuum and mechanical advance. You don't have to have a WOT switch but it's good to have. The wiring diagram for the Lambda circuit is D:04:12. The WOT and Thermal switch share the same wire and they ground it to force the circuit to full. Base (initial) timing is ignition timing, not cam timing. As far as I know, ALL cams are installed to the same timing, ie, you line up all of the marks. OEM cams use 13 degrees BTDC. If you use a "hotter" or performance cam they are usually set a few degrees more advanced, say 16 degrees. If you don't know whose cams are in the car and you don't have the documentation you can experiment with the timing to find the right spot. On a hot day you try advancing the timing till you get pinging (detonation) and then back off 2-3 degrees. This is very dependent on the octane of the fuel you use, lower octane means less advance. More advance means more power but also more heat. Before playing with the timing you should get everything working correctly and in good tune, like a clean air filter, fresh spark plugs, etc.

[Ron]

Ok, I'm back at it now that it's nice outside again. I did the jumper with Dave's solid state relay removed. The car still doesn't start right up. I checked the voltage at the TTS while jumpered and cranking and it hit just over 10V. With the UB not jumpered to ground the TTS only sees about 1V while cranking.

I bought a new TTS from DeLorean assuming it was bad but the new one exhibits the same response as the old one.

The requirements in the test are that the WR wire has battery voltage, 12V+, and the UB wire is grounded before assuming the TTS is bad....
But it sounds like you are onto the problem (low voltage on WR wire).

If you checked the voltage with the TTS unplugged (you should), there should not have been a difference when the jumper is in or out.
Repeat the test with the TTS and CSV unplugged. Record the voltages at both plugs when the key is in the start position. They should be the same (~12V+). If not, I'd need to know if your D had the starter relay wiring modification performed to go further (see service bulletin ST-05-2/82).

[spikeygg]

I measured the direct battery voltage after all testing and it was 12.55V. My VIN is 4796 so I think it should already have the TSB applied.



CSV Troubleshoot.png

What could be the cause of the voltage drop at the CSV and TTS with the HSR-UB jumpered?

I'm looking at the big colorful wiring diagram and with the TTS and CSV disconnected the WR wire seems to only hit the ignition switch, the starter, the starter relay and the hot start relay.

[DMC5180]

I measured the direct battery voltage after all testing and it was 12.55V. My VIN is 4796 so I think it should already have the TSB applied.



CSV Troubleshoot.png

What could be the cause of the voltage drop at the CSV and TTS with the HSR-UB jumpered?

I'm looking at the big colorful wiring diagram and with the TTS and CSV disconnected the WR wire seems to only hit the ignition switch, the starter, the starter relay and the hot start relay.

Have you done a source voltage check at the start inhibit relay? Pull the relay and ensure all terminals are in place ( none pushed out) trust me it happens. Supply voltage should be socket terminal 30. If thats good. Move to the bulkhead connector. (White 7 way connector) unplug it and test voltage on the pin (key in start position) if thats good. Just the act of disconnecting and reconnecting a couple times can fix a poor connection here. Note: The W/R wire splits in the Engine bay harness side BH connector. These are 2 unique W/R wires. The wire to the CSV has a spiraling (candy cane) Red stripe. The other W/R wire has the typical parallel Red tracer.

[Bitsyncmaster]

I measured the direct battery voltage after all testing and it was 12.55V. My VIN is 4796 so I think it should already have the TSB applied.



CSV Troubleshoot.png

What could be the cause of the voltage drop at the CSV and TTS with the HSR-UB jumpered?

I'm looking at the big colorful wiring diagram and with the TTS and CSV disconnected the WR wire seems to only hit the ignition switch, the starter, the starter relay and the hot start relay.

Are you jumping the UB wire in the hot start relay socket to the black wire in the hot start relay socket?

The CSV only gets power when the starter is cranking (the white/red wire).

[Ron]

I measured the direct battery voltage after all testing and it was 12.55V. My VIN is 4796 so I think it should already have the TSB applied.



CSV Troubleshoot.png

What could be the cause of the voltage drop at the CSV and TTS with the HSR-UB jumpered?

I'm looking at the big colorful wiring diagram and with the TTS and CSV disconnected the WR wire seems to only hit the ignition switch, the starter, the starter relay and the hot start relay.

Good job...
Assuming the key is start position and Dave's hot start relay is removed (as directed ;-), your chart shows that the TTS is not grounding the UB wire and that the WR wire, from the starter relay, is not supplying enough voltage to the TTS or CCV (and probably not to the hot start socket, fwiw).

Odd, but it seems like the TTS is bad (or its case is not grounded...) and relay pin 30/51 is not getting 12V from the fan breaker (or maybe a bad relay).

You should have this:

ug.jpg

[spikeygg]

Have you done a source voltage check at the start inhibit relay? Pull the relay and ensure all terminals are in place ( none pushed out) trust me it happens. Supply voltage should be socket terminal 30. If thats good. Move to the bulkhead connector. (White 7 way connector) unplug it and test voltage on the pin (key in start position) if thats good. Just the act of disconnecting and reconnecting a couple times can fix a poor connection here. Note: The W/R wire splits in the Engine bay harness side BH connector. These are 2 unique W/R wires. The wire to the CSV has a spiraling (candy cane) Red stripe. The other W/R wire has the typical parallel Red tracer.

I just pulled the white 7-way bulkhead connector and with the start inhibit relay in place, I see 12.8V at pin 32 while cranking. I see 13V at the brown wire going to the start inhibit relay. As well, none of the pins appear to be pushed through.

[spikeygg]

Are you jumping the UB wire in the hot start relay socket to the black wire in the hot start relay socket?

The CSV only gets power when the starter is cranking (the white/red wire).

Yes, jumping the UB to black in hot start relay socket with the solid state relay removed.



IMG_20200412_161852.jpg

[spikeygg]

Good job...
Assuming the key is start position and Dave's hot start relay is removed (as directed ;-), your chart shows that the TTS is not grounding the UB wire and that the WR wire, from the starter relay, is not supplying enough voltage to the TTS or CCV (and probably not to the hot start socket, fwiw).

Odd, but it seems like the TTS is bad (or its case is not grounded...) and relay pin 30/51 is not getting 12V from the fan breaker (or maybe a bad relay).

You should have this:

ug.jpg

This is a photo of the back side of my start inhibit relay. I think I can see the modification, one of the old wires was cut and a RW wire was run in its place.



IMG_20200412_160757.jpg