Cold start problem

1970 Volvo P1800E.  Cold start system does not use a thermo-time switch but rather a thermo-relay in the ECU which grounds the cold start relay. Relay test good and power present while cranking to relay.  Coolant temp. reading verified at ECU and accurate.  ECU is not grounding the cold start relay.  

Has anyone seen this?  Common?  Internal ECU fault with thermo-relay?

Thanks
 

Hi Unknown,

please have a look at our Netiquette .

Depending on version of your ECU it has this electronic thermo time switch or not. So what is your ECU no?

Hello,
Apologies for my blunt entry. My name is Kurt and I am an owner/operator of a Volvo specialty shop in Santa Fe, New Mexico, USA. I have enjoyed this forum and its well of information in helping with various shop work.

My ECU has a sticker that shows it to be a remanufactured unit by Bosch Volvo of America Corp with the following numbers on it:

5-243315
0280 000 034 094
224705

I am referencing the Robert Bosch D-Jetronic workshop manual for Volvo.

Hi Kurt,

that is what I feared. If you look at my chapter 3.9 of ECUs you will notice that there are various ECUs for Volvo. Column "Coldst" shows that your ECU 0 280 000 034 is without electronic thermo time switch. It is for cars with external thermotime switch. You need 0 280 000 017 or 009 with 0 280 100 010 MAP sensor. Or you install a VDO thermotime switch and ensure 0 280 100 035 MAP sensor.

Hi Curt,
the 0 280 000 34 ECU is a newer type without the cold-start-function and without the shut-off at decelleration.
It doesn't fit the car...
Look a the ECU - section of Volker's compendium and you will find the unit that fits the car.

Regards
Norbert

edit: Volker is faster than me...

Hi Norbert and Kurt,

correct 0 280 000 034 does not have overrun-shutoff. But that does not matter a lot - only in fuel consumption. But missing electronic cold start feature lets the car start badly when cold. And combination with MAP sensor must also fit.