Wiring confusion for thermo time switch and cold start valve

[lsoasey]

My car has a cold start issue which I'm fairly certain stems from a problem in my cold start valve circuit. Here what I have observed thus far:

- I've preformed the "plug swap" a few times now and it immediately resolves the cold start issue. (Conclusion: The Cold Start Valve (CSV) is good)
- I've unplugged the Thermo-Time Switch (TTS) and made measurements between ground and the two connectors. I get something around 34 ohms on one pins and nearly zero ohms on the other. (Conclusion: TTS is probably good -- I know this is doesn't prove out all failure modes of the TTS, but I think it at least shows that it would provide a ground path for the CSV.)

With a price tag north of $100, I'm hesitant to just try buying a replacement TTS to see if that fixes it. Instead, I set to work looking for potential wiring issues. I unplugged the bulkhead connectors, pulled back the applicable connector sheaths, and started probing with my multi-meter. (I should also note that I'm using the colorized schematic PDF as a reference which I found elsewhere on this forum.) I was able to prove out what appears to be good wiring for the Blue/Black wires on both the CSV and TSS to the white bulkhead connector closes to the rear of the car. I also could test for a good connection on the White/Red wire from the CSV to the white bulkhead connector closest to the firewall.

Where I started to get confused is at the other terminal of the TTS. I see a Blue/Yellow wire attached to this position of the TTS connector. The schematic shows, however, that it should be a White/Red wire -- basically the same one connected to the CSV. Here's a snippet of the schematic to illustrate:

41444

Now, it appears that my Blue/Yellow wire goes to the blue bulkhead connector at pin 24. (Referencing the "DeLorean Bulkhead Connectors" PDF also found on this forum.) The multi-meter confirms this. The Bulkhead Connectors document includes this note in the description for this pin: "To starter connection for ignition resistor bypass relay in engine compartment" Based on the schematic, I think this particular wire also connects to the starter motor, similar to the White/Red wire, but to a different terminal. I'm not sure what the difference is between the two connections at the starter... Clearly my wiring is inconsistent with the schematic, at least for this detail.

Does anyone have some advice for how to sort this discrepancy out? Is there anything else I can do to isolate issues in the wiring or other components within this circuit? Should I give up on this path and just buy the replacement TTS?

Thanks!
-Luke

[Bitsyncmaster]

When I first got my car, the CSV would not fire. I found my wiring did not match the schematic either. I did find the problem in that jumper in the bulkhead connectors (backside between two connectors) was reading about 50 ohms. I rewired it to not use that jumper and it fixed the CSV problem.

I have since removed my TTS wiring and now use my hot start relay to fire the CSV when needed.

[Kukem]

I have a few discrepancies as well when I look at the wiring in the car. My car also has a cold start issue, but I have rigged up a switch to the white connector in the relay compartment close to the firewall. It seems to act like the plug swap while the switch is pushed. It helps until I can save up enough cash to justify the TTS replacement. It appears that it is not uncommon for the TTS to go bad. Others have much more experience with this stuff, but by rigging up the bypass, it will allow you to enjoy the car as you continue to work things out.

[David T]

I have a few discrepancies as well when I look at the wiring in the car. My car also has a cold start issue, but I have rigged up a switch to the white connector in the relay compartment close to the firewall. It seems to act like the plug swap while the switch is pushed. It helps until I can save up enough cash to justify the TTS replacement. It appears that it is not uncommon for the TTS to go bad. Others have much more experience with this stuff, but by rigging up the bypass, it will allow you to enjoy the car as you continue to work things out.

One quick way to kill the TT switch is to force the plug onto it incorrectly. Because it is not just a switch but also has a timing element built into it, you can damage it. A simplified schematic is in your Workshop Manual on D:04:06. The wiring was modified and not all cars have the connection between W/R from the TTS to W/R on the CSV. Instead W/R from the TTS goes to U/Y on the starter. Make sure nothing is plugged into the hot start relay plug and prove out the wiring. If it all checks out you probably will need the TTS. One quick thing to check is to make sure the TTS switch is actually grounded. It threads into the water pump and is sealed by a copper washer. I once saw a car where they used teflon tape and it insulated the TTS from ground preventing it from working correctly. Just use an ohmmeter and check for continuity between the body of the TTS and the water pump. Then check for continuity between the 2 terminals on the TTS, it should be 0 when cold. Then check U/B to the case, that should be infinity and W/R to the case should be something high but not infinity and not 0. As for the CSV, easy to check, just pull it off, stick it into a bottle, do the plug swap and watch it spray when you turn on the ignition. Don't lose the tiny "O" ring on it or you get a vacuum leak that is very hard to find!

[Kukem]

"Great Information Here!"

Thanks, David. I will try that this weekend. Right now I am fighting with my fuel filter from hell. I am always game to trouble shooting anything before dropping money. (just like the OP)

[lsoasey]

The wiring was modified and not all cars have the connection between W/R from the TTS to W/R on the CSV. Instead W/R from the TTS goes to U/Y on the starter.

This bit is interesting... David, do you happen to know if there are specific advantages with the modified wiring? (W/R wire connecting to both the CSV and the TTS) It seems like one possible issue in my circuit is that it may not be getting +12V while the ignition key is in the start position. (I haven't tested that with a meter yet... Probably should.) These is the leg of the circuit which provides that the +12V to those two components. I should also ask this: Can you tell me any more details about the U/Y wire connection to the starter? I would assume that this would supply +12V only while starting (similar to what I would expect from the W/R wire), but I'm unfamiliar with this particular terminal.


One quick thing to check is to make sure the TTS switch is actually grounded. It threads into the water pump and is sealed by a copper washer. I once saw a car where they used teflon tape and it insulated the TTS from ground preventing it from working correctly. Just use an ohmmeter and check for continuity between the body of the TTS and the water pump. Then check for continuity between the 2 terminals on the TTS, it should be 0 when cold. Then check U/B to the case, that should be infinity and W/R to the case should be something high but not infinity and not 0.

Good advice here... I'll make those measurements in the next day or so.

[lsoasey]

When I first got my car, the CSV would not fire. I found my wiring did not match the schematic either. I did find the problem in that jumper in the bulkhead connectors (backside between two connectors) was reading about 50 ohms. I rewired it to not use that jumper and it fixed the CSV problem.

I have since removed my TTS wiring and now use my hot start relay to fire the CSV when needed.

That's an interesting find... I'll see if I can check out that jumper on my connectors also. Thanks highlighting that one.

[David T]

That's an interesting find... I'll see if I can check out that jumper on my connectors also. Thanks highlighting that one.

Somehow, someway, you need +12V on the W/R terminal of the TTS during cranking and ONLY during cranking. Easy to check. BTW there is another simplified schematic on D:01:10. If anyone ever touched the starter wiring they could have messed up the power to the TTS.

[Ron]

Somehow, someway, you need +12V on the W/R terminal of the TTS during cranking and ONLY during cranking. Easy to check.

+1

There are more than one version for the harness (one even has two plugs that fit the TTS...).
This link may help: http://dmctalk.org/showthread.php?4912-White-Trapezoid-Plug-with-U-Y-amp-U-B-Wires-ID

[lsoasey]

I finally had some time this weekend to continue diagnosing my potential CSV/TTS issue. I'll have to admit, however, that I'm a bit confused now. I spent time tracing out wires and looking for potential broken or high resistance wire links, but I didn't identify anything suspicious. I also made various voltage measurements while cranking the engine. (I had the coil unplugged to prevent starting.) Here are some of my observations:


Voltage at the CSV is around 9.24V while cranking.
Voltage at the starter is around 10.10V while cranking.
Voltage drop between the positive terminal of battery and the starter is around 0.15V while cranking. (Acceptable drop, I believe...)


I wasn't sure if 9.24V at the CSV was enough for it to open, so I also pulled the CSV and placed it in a glass jar. It produced fuel when cranking cold, although, I don't really know if it was a normal amount a flow. Are these Cold Start Valves either completely on or completely off? In other words, could it inject less fuel if it was getting a lower than normal voltage while cranking? Also, what kind of voltage at the starter is normal while cranking? I know it pulls a lot of current, but I don't know what voltage level to expect assuming that my battery is healthy. (I think it is...) There seems to be a voltage drop between the starter and the CSV that I didn't expect...

So... Now what? I thought that the plug swap technique was always improving my cold start issue, but now I am in doubt. Perhaps I unknowingly fixed a wiring issue while unplugging and re-plugging connectors? I'll have to wait until I experience the cold start issue again in order to test the plug swap technique to confirm or deny the behavior I originally reported. Finally, I realized later that I was focusing on the positive side of this circuit and not really looking for grounding issues. Should be chasing bad grounds next?

[Bitsyncmaster]

The CSV is all on or all off. I do think your 9 volts is enough to open the CSV. Remember the CSV only works if the engine coolant is below 95 deg. F. So when your engine is above 95 deg. the CSV is not working unless you do the plug swap.

[yianni]

Similar problem with my car, after replacing fuel lines my car wont start when cold. Did the plug swap to csv all good there wire read good with meter have 9.8v on csv plug while cranking cold. David said to check tts for resistance to be 0 when cold but mine has 5.4, on page D:01:10 shows arm closed cold, to provide ground to csv. The funny thing with all this is the car started and ran fine before new fuel lines where installed maybe I messed up somewhere thanks for any advice.

[yianni]

Found out that Alfa Romeo uses same TTS so I pulled mine out of my Spider that I know works and plugged it into the D but still didn't fire up the CSV, maybe wiring problem or something that am not seeing. Read on the UK forum that some cars function ok with out the TTS (working) maybe mine was that way and I never knew it, so when I replaced fuel injection lines something changed in fuel pressure and now it will not start cold unless you spray with starting fluid. Can I bypass TTS so CSV will fire? does anyone have a detail way of doing this? Or is this a combine problem with the CO mixture that I need to readjust? Thanks for any response, don't have other D owners in this area to exchange thoughts other than this forum, Thanks again.

[Bitsyncmaster]

Found out that Alfa Romeo uses same TTS so I pulled mine out of my Spider that I know works and plugged it into the D but still didn't fire up the CSV, maybe wiring problem or something that am not seeing. Read on the UK forum that some cars function ok with out the TTS (working) maybe mine was that way and I never knew it, so when I replaced fuel injection lines something changed in fuel pressure and now it will not start cold unless you spray with starting fluid. Can I bypass TTS so CSV will fire? does anyone have a detail way of doing this? Or is this a combine problem with the CO mixture that I need to readjust? Thanks for any response, don't have other D owners in this area to exchange thoughts other than this forum, Thanks again.

I sell a HOT START relay that will bypass the TTS as long as the wiring is working. I run my D without the TTS.

[David T]

The wiring is pretty simple. Go to D:01:10. Common things to look for:
Plug to the TTS damaged and forced on incorrectly
Someone screwed the TTS into the water pump with teflon tape insulating it from ground
The starter was removed and replaced and the wire to the CSV was not put back right
Something is plugged into the hot start relay plug (nothing is supposed to be plugged into it).

If the wiring is messed up you can damage the TTS. It is very rare for there to be a problem with the CSV itself.
I would start by checking for 12 volts at the CSV when cranking.

[DMCMW Dave]

. Can I bypass TTS so CSV will fire? .

For testing purposes only:

Locate the unused relay socket in the electrical compartment (the one hanging by wires at the back of the compartment). It has three wires going to it; black, black/blue, and white/red. Install a jumper between the blue/black and black wires. DO NOT EVER connect anything to the white/red wire. With this jumper in place the cold start valve will spray as long as you have the starter keyed. It will not "time out" as it would with the thermotime switch, but it will only fire during cranking.

This will make for a car that starts fine when cold but it will tend to flood when hot, so you really don't want to just leave the jumper there all the time.

[novadmc]

The CSV is all on or all off. Remember the CSV only works if the engine coolant is below 95 deg. F. So when your engine is above 95 deg. the CSV is not working unless you do the plug swap.

given this, does this mean that if it's a particularly hot day (95+), and the car's been sitting all day, if you try and start it "cold" (but ambient temp, and thus coolant temp) is above 95 deg. F, you mightsee the car slightly struggle to turn on?

[Bitsyncmaster]

given this, does this mean that if it's a particularly hot day (95+), and the car's been sitting all day, if you try and start it "cold" (but ambient temp, and thus coolant temp) is above 95 deg. F, you mightsee the car slightly struggle to turn on?

I guess that could happen. But with my car, I only need the CSV if the car has been sitting without running for a week or more.

[whocruiser]

given this, does this mean that if it's a particularly hot day (95+), and the car's been sitting all day, if you try and start it "cold" (but ambient temp, and thus coolant temp) is above 95 deg. F, you mightsee the car slightly struggle to turn on?


I guess that could happen. But with my car, I only need the CSV if the car has been sitting without running for a week or more.

Dave, I was seeing exactly that situation here this summer down here in Florida in our current heat wave, and had sometimes seen it in past summers, without making the mental connection to the CSV being involved at that time. Since I put your Hot Start Relay into VIN 1150 a few weeks ago, I've been starting great under all conditions.

[novadmc]

I guess that could happen. But with my car, I only need the CSV if the car has been sitting without running for a week or more.

that was the scenario i think i was in a few weeks ago. when we had that 95-100 def F heatwave, i was finding the car struggling to turn on in my garage in the afternoon after it sat for a week. 1st crank it would die. 2nd crank it was fine. drove fine. turn it off, fires right back up fine. hasn't done it since (tho i also *slightly* adjusted my mixture around that time too, so i might have been just a tad rich on startup too before doing that.

either way, the last few times i've fired up the car, its been well below 95F again and its fired up cold just fine. i dont know about you, but im ready for September weather already around the DC metro area :)

[yianni]

Thank you all for this information. I did what you all suggested first (jumping black, with black/blue wire) and car fired up just like it use to and ran fine. Then I checked for continuity from the starter (red /white to the TTS plug red/white) it checked out good, then I checked for volts on the TTS plug while cranking (car disabled) it measured 9.8v probably enough to activate switch, so my thinking is bad TTS, right? Still don't know why it started fine before new fuel lines were installed and now it needs the CSV to kick in every time it's cold (like 4 to 5 hours).