Hello all I'm about to loose my mind. My 91 940 Turbo just will not start. I went onto the 7/9 Faq page and looked up all the No Start info i could find. I can hear the fuel pumps coming on i also pulled the return line off the fuel rail and fuel was present in the rail. I checked the Radio suppression relay it to seems fine i have voltage on all the leads. I also checked the fuel pump relay i can hear and feel it click when i turn on the ignition. I also checked the voltage at the Injector Ballast i have 12 volts on all the leads. I also checked for voltage at the injectors i have 12 volts on both the leads there also. So after making sure that all the voltages were correct i assumed that maybe it was the Crank Position sensor was bad so i went out and purchased a new one from Volvo and replaced it STILL NO START AAARRRRRR!!! I am out of ideas here i need HELP... I am left feeling that it just might be the ECU is bad hopefully not, any way to test the ECU to see if it went south for the winter??
By the way the car does have 300k miles on it so could it be anything that wore out that i am not aware of?? Any help will be greatly appreciated thanks, SAUL

PROBLEM SOLVED!!! Thank you guys for all the help my car is alive again. I came home and bypassed the Radio Suppression Relay and the car fired right up!!!
The thing that gets me though is this, i tested that thing several times and it always tested perfectly fine. The solenoid works fine and the contact is made, but yet it will not flow electricity very strange. I will try soldering the board today to see if it works better, but the there are no dark burnt sections on it and all the solder points are all still in great shape. VERY STRANGE!! Once again THANK YOU, all of you for your help!!!!! I hope someday i can repay you guys, if any of you are ever in Southeastrn MA heading out to the CAPE area let me know we'll do Lunch.... SAUL

From what you have said:
spark OK at plugs
Fuel rail pressure present
12V to injectors

The prime suspect now is the radio suppression relay. A static test for 12V does not mean it is working. When the load of the injectors firing is applied a bad solder joint can kill the 12V output from it. Resolder it. You also said there was 12V at every lead. That would not be normal because one lead goes to ground.

--
David Hunter

Well, yesterday was a very busy day around here with my sons baptism and all, but I did try one thing. I did the component test recomended by WOng3 it seems to me that my assumption is correct the injectors are not firing. The very first step in the test is to fire the injectors the LED flashes very quickly but no clicking from the injectors. I performed the test several times, and one of the tries the injectors fired for maybe 2 seconds. I quickly shut off the car and unplugged the OBD and fired the car up it ran for 1 second.
So today when i get home from work i am going to do the following i am going to Bypass the RSR and the FPR with some wire pigtails to simulate properly working relays and see what happens. I hope this does the trick and that way i can figure out which one is the culprit. Now, what do i do with this $60 crank sensor i have here that i already put in the car the dealer probably will not take it back? Anybody need a CPS for a 940 turbo out there??? Once again thanks to all of you for the info it is greatly appreciated. SAUL

I was thinking the same thing that dave said about voltage at both leads, unless there is no ground when measured.

Did you run the diagnostic thing where the injectors pulse for 3 seconds, the idle speed motor clicks 3 times... etc, etc? Try that to make sure the injectors are pulsing.

Resolder the fuel pump relay and the radio suppression relay anyways.

It's probably not the temp sensor, as I found that when one went bad in the 940, it was hard to start, but not impossible.

Any error codes from the system?

Sounds like you might want to check spark, like the other guy said.

You may also want to check the fuel pressure.

Greg

I am going to try that diagnostic thing, also there are no codes i tried that already. I also checked spark and that is fine also. If it were the coolant sensor wouldn't it throw a code? As for fuel pressure i do not have a gauge,but i tried a different method by simply disconnecting the return line at the fuel pressure regulator and cranking over the motor and fuel came out of the line with some pretty strong pressure strong enough to reach the firewall of the car. One other thing i tried was putting a screwdriver on the injector and putting my ear to it while someone cranked the motor over and i could not hear the injector firing. That is when i started testing the fuel and suppression relay's and they tested to be in fine working order so that is why i went with the crank sensor to no avail. I sure do hope it is not the ECU!!!! BTW do you know if the ECU out of an early 85 thru 89 740 turbo will work on my car?? The local junkyard has about six of them that i can get the ECU out of but no 940's :( Thanks SAUL

Saul,
I have a 91 940 turbo with 200k and any starting problems have been related to what you have checked. You indicate that you have fuel, however, did you check for spark? Pull the coil wire out slightly and have someone crank or pull a plug wire and attach an extra plug to it, ground the outside and see if you get about 1/4" spark jump to ground.

A more rare thing would be the coolant temperature sensor, but with 300k ...

If your injectors are not buzzing, then how about your power stage unit mounted on the drives side of the fender wall just aft the battery? I just bought one yesterday for $80 for my 86 740 with 200k.

I'm no expert, but have been there with an intermitent no start, had several mechanics attempt to fix and could not, and I found myself to be radio suppression relay. To double check, swap with radiator fan relay (same relay).

One more thing. Is it could were you are? I have had a starting problem when weather turned very cold, and turned out to be spark plugs. I did not get any firing of cylinders, just turned over.

If you have never replaced your fuel or radio suppression relay. It may be a good time to re-solder the boards or buy new relays.

Power stage unit???? Do you mean the injector ballast mounted on the inner fender well? I did check the ignition and all is fine the coil is firing, spark plug wires are ok and so are the plugs. I also tried pulling codes out of it and that came up clean also. I also have an electrical background so i feel pretty confident after testing it that it is not the radio suppression relay. If it were the coolant sensor wouldn't it throw a code saying so?? Thanks SAUL

I don't know about the code for the coolant sensor. Power stage is for ignition coil and is mounted on fender well just behind the battery. Does not matter anywhy if you have spark. You say you have power to the radio suppression relay, but is the relay itself working? This was my problem. New one was $25.00, and some have resoldered them.

Yes the Radio suppression relay is working just fine i hear it click when i turn on the ignition and i have 12 volts on both the main leads coming out of it. This sure is getting fun !!!!! SAUL

Feels gooood doesn't it. I know what you went through.
Gary