Hi,
(I have a 90' 760turbo)After going thru the 700 FAQ and what was suggested.. I've replaced The ignition control module and RPM sensor. On a whim I also replaced the ignition switch. Still no spark at all. Tested coil by wiring direct to battery and get spark. I see to check the fuel and radio suppression relay.. But where are these? They aren't in the relays behind the radio.. But when I do turn car on the fuel pump does come on.. Car still will turn over (Battery is charged) still not start b/c no spark. What else is there to check? The computer itself? ideas??


thanks,tom
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90 Volvo 760 Turbo, 86 Mercedes 300E,87 Maserati Biturbo,95 Hummer XLC

It sounds similar to a problem I had with my '86 760 Turbo. It was a device called a Power Stage which is basically a signal amplifier about the size of a regular bar of soap. It amplifies the little signal from the ECU into the strong signal needed by the coil. It's output was shorted. It died while idling in my driveway. Thank goodness it didn't go when I was on the freeway. With the hood open you can see it mounted on the left fender up near the front. It cost me $100 a couple of years ago and required some heat sink compound when I put the new one in.

Hi,
I have replaced the "power stage" with a new Bosch one. The power stage is also know as the ignition control module.. (The part right above the battery thats heatsinked to the fender that amplifies the ecu signal)

At this point I swaped the relays on the strut tower with each other.. the fuel pump still comes on.. Turns over with no problem but doesn't catch. Still no spark. The only other thing I can think of is the computer itself? its almost like the ignition computer is unpluged or something.. (maybe loose, before under certian loads the car would just turn off before.. not starve as if it were out of fuel)

Is the fuel and ignition computer in the same unit? or is it just the fuel computer on the passenger side floor.. and ignition computer under the drivers side dash?

tom
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90 Volvo 760 Turbo, 86 Mercedes 300E,87 Maserati Biturbo,95 Hummer XLC

Have you replaced the ignition power stage? It's plugged into the LF fender, and it's certainly a likely cause of no spark. I think they run about $75 new. Perhaps a junkyard module can be had for $5-10 to try it out.

Good luck!
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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '84 242DL/AW70-100K, '89 244DL/AW70- 212K and I miss my: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K

The fuel pump relay is in the cluster behind the ashtray and fuses. The radio supression relay on my '91 Regina is under the hood on the passenger side strut tower. But if your fuel pump is running, neither of those are your issue.

How are you determining no spark?

I had a no start that turned out to be fouled plugs. A new set of plugs started it right up, but I still had to figure out why my plugs were getting fouled. That probably isn't your problem, but might be worth a try since new plugs are only a few bucks.
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Andy in St. Paul, '91 745 Regina 198K mi, '89 244 142K, '87 245 RIP

I determined spark by taking a screw driver to the coil, turning car over while taking the plug from the coil to the screwdriver itself.

I will check the plugs.. did a tune up not less then 5k miles ago.

thanks
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90 Volvo 760 Turbo, 86 Mercedes 300E,87 Maserati Biturbo,95 Hummer XLC

radio suppression relay is seperate from main relay. fuel pump running does not mean radio suppression relay is good! swap with fan relay which is either next to our across from radio suppression relay (on strut tower or radiator overflow resevoir)

If a bad radio suppression relay doesn't shut off the fuel pumps, then what does it shut off?

I don't know about a '90 turbo, but I searched for a radio suppression relay on a friends '89 740 8 valve and it was not with the fan relay. In fact, I finally concluded it didn't have one. On my '91 740 Regina, the two black relays are together on the strut tower.
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Andy in St. Paul, '91 745 Regina 198K mi, '89 244 142K, '87 245 RIP

Standard model won't have one, until 1991 (I think). The 89 Turbo should have a radio suppression relay, though for a 760 I'd have to reference the relay location guide in the FAQ. THe 740T has it right in the fuseblock on this car.

760's are a little different with their fuses in the driver's side of the dashboard and relays on rails.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '84 242DL/AW70-100K, '89 244DL/AW70- 212K and I miss my: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K

I am having a similar problem with my car. When it is cold the engine will start. After it has warmed up, if I turn the car off and come back while the engine is still warm the car will no longer start. I replaced the coil because I had no secondary to primary resistance. I am still having the same problem and now it will not start at all. The starter is working just fine and the engine is turning but it feels like there is not enough voltage to get the car going. I do not think that it is spark plug related because I have no problems once getting the car started. A friend of mine suggested that I swap the cooler fan relay and the radio supression relay because they use the same part number. Unfortunately, I cannot find those on the diagram for the relays in my repair manual and have not found anything online. What is the fuseblock and strut tower? Thanks for the help

Uh yeah, of course I hit enter before reading "760" - haven't even had any champagne, since I'm at work. It's under the right side of the dash if I'm not mistaken.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '84 242DL/AW70-100K, '89 244DL/AW70- 212K and I miss my: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K