928 S4 won't start when cold without starting fluid
 

A S4 that will not start without a few squirts of ether and then runs rough for a bit until it warms up. THen it runs great and idles fine.
Tried jumping the XX relay to keep the pumps running before trying to start it but made no difference.
Once it has warmed up, you can drive it anywhere and as hard as you want, then stop it and it starts right back up like it should.
Have not checked fuel pressure but figured that would cause other problems if it was an issue.
This car runs like new once you get it started.

Any ideas?
Thanks

when was the MAF rebuilt same for the LH computer,
and when were the dampers and FPR swapped out,
and when was the intake refresh done

Not sure of the answer to any of those but why would it run so well once warmed up? Wouldn't some of those cause other issues?

is this car supercharged?
remember the more info you can add the better the guesses will be

Bone stock. No mods of any kind 1989 automatic

Sounds as though you need to check the resistance values for the LH channel of your temp2 sensor.

To do this pull the LH plug off the computer and measure the resistance between terminal 13 and either terminal 5 or 17 [both earth]. When cold you should see values around 5k ohms and when hot about 100 or so ohms.

If the value you measure hot or cold is the same and frozen at around 100 ohms or so then the LH will not enrich the fuelling for cold starts.

I was going to guess the Temp II sensor as well.

They are a wear part and should be replaced either with every timing belt or 10 years.

When my Temp 2 failed, the car would start easy with the sensor unplugged. May be an easy check.

Also, smell the vacuum connectors on the fuel pressure and damper valves. When they failed the starting symptoms were similar to the failed Temp 2.

Pulling the temp2 connector causes the brains to think that the coldest setting is required [infinite resistance] and it will default to such when cranking and if that works a pretty good sign that the temp2 is toast without having to measure anything..

For those of us with ST2 we simply hook up the laptop and see what value of temperature is shown in both the LH and EZK channels - one presumes the OP does not have such facility.

What is a "ST2"? will it work on an 87?

Please post a few pictures of the engine bay

ST2=Sharktuner version 2. This requires modifications to the LH and EZK computers that have to be fitted with programmable eeproms. One also needs the interface kit plus a laptop.

Thanks for all of the replies. Where is the temp 2 sensor located? I should know that but haven't been doing any
928 work for a while
.I have a ST2 but since this car does not have eeproms in it, I cannot use it on it.

temp 2 is on the right side, (passenger side) of the water bridge
see the blue connector,
2 circuits,
test each pin to ground. they should match,
also the connector can have the wires touch due to shedding insulation,
if its in question replace the boot and connector.

https://cimg8.ibsrv.net/gimg/rennlis...dfbb7fa7a7.jpg

Temp Sensor II is the problem.

Had this happen to my S4 when i first bought it. When extremely cold, the sensor would open loop sending the LH into coocoo mode. Hard to diagnose since when warm, the range of resistance was normal!

Thanks. I remembered where it was right after i posted. I actually have one I can test it with when I get the chance

When Temp 2 or its wiring are faulty, the LH defaults the fuelling to the normal running 80degC settings. This is too weak to start a stone cold car. Unplugging it may work if it's just the sensor that is faulty, but is there's a short on the temp 2 connector or harness you wont get the desired open circuit for a cold start.

Thanks! I plan to check it where the signal comes to the ECU.
Aren't you the ST2 guy that sold me one through the guy in Washington? His name slips my mind

Yes, Jim Corenman in WA is the worldwide agent for Sharktuners. He gives fantastic support as he is a very skilled user. I have retired from JDSPorsche, which is being now run by Mike Parris here in uk and its agents worldwide. But only Jim Sells Sharktuners:-. SharkTuner – A complete tuning system for the Porsche 928 and siriuscyber.net/sharktuner/

Mr. Merlin.....have you ever thought about offering by the hour virtual "guidance"? I would guess that you could book some serious revenue just using video conferencing...the customer would be able to use his video from his phone and you could walk him through the steps from the comfort of nice office chair. I designed a system back before the days of iphone/facetime that allowed engineers that would normally be at a well site in North Dakota, overseeing operators of a single well, to work from an office and oversee 5 wells without travel. The biggest problem we had is that the guys on the well would touch the camera lenses.....otherwise, it was awesome.

Take money, inherit liability.

Sad, but most likely true.
I'd also appreciate such a service.

I have done PP consulting events,
most will return for more advice and guidance,
this usually results in a positive outcome for the owner.
If your willing to turn the wrenches,
Its way cheaper than flying out a mechanic.

I am at a point of potentially having to find and fly a mechanic to Saudi to do service on my and 2 other 928s. It’s a tough to service this car here.

^^^ what type of work do you need?
I just got my passport renewed.
Do you have a well stocked toolbox?

The two wires to the temp II sensor were shorted together.
THanks

I have a similar situation with a 89 S4. Car wouldn't start. Finally, having read this thread shot starter fluid into the MAF and sure enough the car started and after warmup it would continue to start.

But, my adventure has taken a dark turn.

While adjusting the wires to the Temp II sensor the wires at the sender began to smoke. After I changed my shorts I pulled the melted harness connector and Temp II sensor.

This is what they look like.
https://cimg1.ibsrv.net/gimg/rennlis...d2e3bf8446.jpg
https://cimg3.ibsrv.net/gimg/rennlis...9d2e961f5c.jpg
https://cimg8.ibsrv.net/gimg/rennlis...492b61685b.jpg
https://cimg1.ibsrv.net/gimg/rennlis...a20e0cd16f.jpg

I repaired the harness connector hoping the no start condition would be fixed. No such luck.

Fearing that the LH had been damaged I tested it in another car and it worked. Whew.

That leaves me with the possibility the two harness wires are shorted in the harness.

To prove this I need to know where the two wires terminate. I looked at the LH connector layout and could not see the Temp II referenced there.

I looked in the WSM wiring diagrams and could not locate the Temp II sensor.

TIA

Can somebody point me to where the Temp II sensor is and even better where it terminates.

thats an ugly connector and sensor ,

make sure the water bridge is not powder coated otherwise you will lose the sensor signal to the computers.
make sure to remove that sealant as well ,
the sensor needs a good ground to work

NOTE posting a few pictures of your engine bay helps us help you

Terminal 13 on the LH module to ground. Should read 5000 ohm cold and almost no resistance when hot. Or so I have heard:roflmao:

NOTE that Temp 2 sensor feeds both computers with a separate signal ,
thus each pin sends a signal to the LH or the EZK. the sensor needs a good ground.
to check the sensor,
test the resistance of each pin to ground. They should match
then at the BOTH of the computer connectors,
find the temp signal pin and the ground ,
with the connector connected to the sensor the computer numbers should also repeat what you find at the sensor

Cold start problems with LH-based 928s

When troubleshooting, always start with the "easy" and inexpensive items first and work your way to eliminate problems until you end up to the difficult and expensive items. The majority of electrical problems are connection related.

If the ECU doesn't know that the engine is cold, it does not provide cold start enrichment and it will not start. Eventually after cranking enough, there may be enough "raw" fuel sprayed into the intake to start the engine. You would see smoke after starting because the fuel wasn't metered properly.

The Temperature Switch II is located in the front center of the engine just to the right of the fuel pressure damper.

1. Check the plug to the sensor, is it on tight? Are the contacts clean? If not, clean the connectors and clip it on tightly. Check engine starting now. If it does, you're done. If not got to step 2.

2. To check the temperature II sensor, you'll need an ohm meter. Remove the connector from the LH control unit. Connect the ohm meter to pins 2 and 5 of the LH connector (not to the pins on the module itself). The correct value ranges are:

0 C / 32 F: 4.4 - 6.0 k-ohm
15 - 30 C / 59 - 86 F: 1.4 to 3.6 k-ohm
40 C / 104 F: 0.9 - 1.3 k-ohm
60 C / 140 F: 480 - 720 ohm
80 C / 176 F: 250 - 390 ohm

Since your problem is cold start, you could just look for the proper resistance range for the ambient temperature of the cold engine. If the sensor is shorted (zero ohms resistance) the mixture will be too lean and the engine will not start when cold. For problems at other engine temperatures, I'm including all of the resistance ranges for higher engine temperatures. If the sensor has an open circuit (infinite resistance), the fuel mixture will be too rich, the engine will not run when warm, and will be difficult to start when warm.

If the values aren't correct, measure them directly at the Temperature Sensor II. You'll see that there are two prongs on the sensor. There are two separate temperature sensors housed in the one sensor body, one for the LH and the other for the EZK module. Note the orientation of the protruding alignment notch on the outside of the sensor. If you are viewing the alignment notch orientated to the left side, the prong closest to you is the prong for the LH controller and the prong further away is for the spark control module. Clip one of the ohm meter leads to the prong closest to you (LH) and clip the other lead to a ground point [Do NOT connect the ohm meter leads between the two prongs of the sensor]. Repeat the resistance measurements.

If the resistance readings are in the correct range, there is a problem with wiring to the LH controller or the connector itself could be corroded. If the resistance readings are not correct range, the temperature sensor must be replaced.

If replacing the sensor doesn't fix the cold start problem, check the fuel filter, fuel line pressure, injectors etc. Fuel injectors can be removed and tested for flow and flow pattern. There are several shops that provide this service. The problem could also be attributed to bad ground connections. Also, don't overlook potential weak spark conditions. If you've eliminated all other areas, a failing LH controller could be the problem.

Rich Andrade

So, new Temp II in the water bridge and readings are within range.

No continuity when inserting probes into the harness end. I think that rules out shorted wires in the harness itself.

The LH works fine on my cold 88 started right up.

I guess the next step is to check continuity from the harness end to the LH and EZK harness ends.

Well, if I read the wiring diagram correctly, one wire from the sensor goes to the terminal 13 of the LH and the other goes to terminal 19 of the EZK

You are correct sir.

That's where I'm going next.

Cant wait to hear the result!:)

No continuity from either side of the harness to LH or EZK harness end.

So were you testing from the LH terminal to the EZK terminal? THat should be about 5K cold.
What about from the sensor end to the EZK and the sensor end to the LH end?

Temp II harness end to LH harness(13) or EZK(19) end should be continuity, right? That's what I'm testing.

well, one wire goes to each ECU so depending on which wire you are on, if everything is disconnected, one wire will show no continuity to one ECU and the other will show continuity nd vice versa for the other ECU.
How about if you jump the to wires together at the sensor and then test between terminals 13 and 19? They should show a dead short between those terminals and open to ground

Here you go.
https://cimg9.ibsrv.net/gimg/rennlis...9b42af184a.jpg

46 ohms. Might just be some wiring resistance. Will it start cold yet or still a problem?
Open circuit to ground so no grounded wires?

No start cold without starter fluid.

If you plug the connector back in on the temp II sensor and then measure the resistance from 13 to 19, you should read around 5K if the engine is cold. Try that.

Figured it out - it's a hoot.
 

It is very important to have WSM with wiring diagram.

I was repairing the Temp II sensor and wanted to be sure the wires were right. The WSM said they were GN(LH) and GN/RD(EZK)

Well my colors did not match. I looked at the Fuel Cannister wires and they matched.

Now I understand why the shorted wire melted the connector and Temp II switch.

I'll repair both harness ends tomorrow. Bet it starts right up.

Kevin

That is crazy.
Are they close enough together to mix them up? Not looking under a hood right now. to see them

In my defense I did not attach the injection harness. But, I also did not notice the mix-up.

I missed several clues.

It is always more of a challenge to find dumb things done by previous owners. You assume that things are installed correctly.:roflmao:
Reminds me of an Alfa I bought from someone we both know that had the crank sensors hooked up in reverse order which made it not start.

No, this was a problem of my own making. We swapped the harness ends. PO did nothing.

I thought you said you did not connect the harness?

On the S4 if the vent and temp connectors were original then the temp2 is blue the fuel vent is black.

Seeing the temp 2 sensor melted made me think that some voltage was not going to the right place.

NOTE in either case make sure to label connectors before you remove them.

So did it start? Inquiring minds want to know;)

Yes it did.

Glad to hear it. I was afraid that I was going to have to come up there and get it running:roflmao: