Cold weather start problems - 1989 240DL

johnny volvo · Post by **johnny volvo** » 16 Sep 2011, 10:11

I have a situation that started in very cold weather last winter, in which the car wouldn't fire. I finally noticed that the in-tank fuel pump wasn't running on ignition. I jumpered at the fuse box between the hot side of the main pump and the downstream side of the fuel tank pump, heard it running, and the car started right up. As the temperature outside warmed up just a bit (above zero), the car would start every time.

Just recently, our temperatures at night dipped into the lower 40s and I'm having the same problem as I did last winter when it was below zero. The engine turns, but the in-tank pump doesn't start. I jumper the connections, starting the pump, start the car, wait 20-30 seconds and remove the jumper and it's just fine. No problems on restart, once the car has warmed.

My suspicion is that this is the coolant temperature sensor. I had already replaced much of the starting circuit - starter, battery, engine control module, relay - last year. And, as I've said, I've had no start issues all summer.

Question 1: Is it, in fact, the CTS?

Question 2: Is the the sensor located on the engine block, driver's side, with the lead plugging into it?

Question 3: How in blazes do you get that out without breaking, stripping, or otherwise doing something that creates a huge problem that costs loads of money I don't have? I found the sensor for $35, which I can afford, but would appreciate any guidance and advice on how to change it successfully.

Thanks!

Post by **billofdurham** » 16 Sep 2011, 12:38

The CTS does not affect the running of the in-tank pump. This is a priming pump for the main pump and should be running all the time the engine is running. Without the in-tank pump the main pump has to work overtime to pull the fuel from the tank. If the in-tank pump runs when jumpered it points to no power reaching the pump in the normal way. This is either a blown fuse, #4 for the in-tank pump, a broken wire or a bad connection at the pump.

The 1989 240 should be fitted with the On-Board Diagnostic (OBD) unit in the engine compartment. Instructions for its use are pinned at the top of the forum. If the CTS is faulty it should throw a 1-2-3 code. Before taking the sensor out you can check it using an ohmmeter.

240 Coolant temperature sensor test..pdf: (177.66 KiB) Downloaded 236 times

If you do find you need to change the CTS give it a good spray of any releasing oil and let it stand for a while. I have changed these many times and never had any problems getting them out.

Bill.

johnny volvo · Post by **johnny volvo** » 16 Sep 2011, 12:49

Bill,

Thanks, as always for your guidance on this. I will check those connections to the tank pump; I know the fuse is okay.

It still perplexes me why this is happening in cold weather. I can only assume that it may be condensation on a connection.

While I'm picking your brain though, and for the benefit of me and others, if the CTS goes bad, what conditions would it cause?

Thanks again for your detailed response!

Post by **billofdurham** » 16 Sep 2011, 13:37

The CTS feeds information to both fuel and ignition ECUs which then determine the best settings for running the engine. A faulty CTS would result in poor performance and mpg.

Bill.

johnny volvo · Post by **johnny volvo** » 22 Sep 2011, 09:40

Well, I have returned, still perplexed.

Does anyone have the wiring diagram for the starting circuit of the 1989 Volvo 240?

My condition persists. The car starts like a champ in the relatively warm daytime, but let it get a bit cool out (upper 40s) and it won't start without the jump between the hot side of fuse 6 (main pump) to the downstream side of fuse 4 (fuel tank pump).

No Check enginelight and didn't find a code.

And it's only a problem when it's cool.

Any thoughts or wiring diagrams, I'd be grateful.

Post by **billofdurham** » 22 Sep 2011, 13:45

Does anyone have the wiring diagram for the starting circuit of the 1989 Volvo 240?

Why settle for just one wiring diagram when you can have them all for not one penny more?

1989 240 wiring diagrams.pdf: (1.89 MiB) Downloaded 370 times

Now I am perplexed. These diagrams come from a Volvo US publication and show that both pumps work through fuse #4 and position #6 is a lead in from a junction box to fuses # 8, 9 & 10. This is not what is listed in the owner's hand book. However, I have checked the Haynes manual and it is showing the same as the Volvo publication.

Bill.