1997 960 will not start after head gasket replace

dougsbart · Post by **dougsbart** » 12 Jul 2014, 08:07

After I replaced head gasket on 1997 Volvo 960 with coil packs it seemed to not want to start. I cranked over several times for maybe two or three minutes. Just as I was giving up it fired. I figured lifters needed to be pumped up and so I charged battery for a couple of hours. I came back and got the car to fire twice and run for maybe 30 seconds, it sounded good, running very smooth. after it died the second time I went to look for a vacuum leak, could not find one.

Since this time I cannot get it to fire, I am at a loss. The plug on the cam sensor was broken in head removal and I read about this as a problem, so I got one at the junkyard, no change. I do not think there is any fire at all, pulled #1 plug and can see no spark when turning over. I know I saw a procedure to test cam and crank sensor somewhere online, but I cannot find it now.

I know what I have read is the test lead for the coils, the single red wire by the cam and crank sensors, has power. I know if I pull the plug to #1 coil and put a test light to ground on the positive marked side and crank the engine I get power, stop cranking and I hear a click and light goes out. Assuming relay is good. If I put test light on other (negative marked side) side, I get nothing during cranking. So no control to coils? I am really suspect of the cam and crank sensor, but want to test before throwing parts, plus I have read several accounts of AZ part being bad out of the box. I have also read of computer going bad.

Here is my issue, while I know there are coincidences I have a real hard time accepting something just "went bad" at the same time some other repair was going on. In 20 years experience of turning wrenches that has maybe happened once. This is why I seem to be pointed to cam sensor, because wiring and plug were broke. While it started that couple of times, I can accept that the jiggling around screwed it up for good.

At the end of my rope, but have never had to throw the towel in before. Looking for that test procedure or any other advice out there. There is fuel to the rail, I am 99% positive injectors working plugs were wet when I pulled all and turned over engine for 60 seconds after I thought maybe I had loaded cylinders. I am getting a noid light today to confirm injectors.

Also, I do not know what constitutes "bounce" of the tach, but there is definitely shaking movement, albeit small when I crank the engine over, I take this as a good sign to rule out crank sensor, but still want to test.

Any input appreciated.

93Regina · Post by **93Regina** » 12 Jul 2014, 21:20

dougsbart wrote:"bounce" of the tach

I'm old school vehicles (Redblocks, and before), and yours is too new for me.

I would think tach would do more than bounce, if OK; but with individual coils, that may be normal if only one coil was used to trigger tach.

Crank Position Sensor - Recheck to see if its plugged in

Timing Belt or Chain - Double Check timing marks...tension-er applying pressure?

OBD-II - Any Codes?

Some suggest wiring harness can be defective: 960 engine wire harnesses

Ethan Rode · Post by **Ethan Rode** » 14 Jul 2014, 01:33

The tach is computer controlled. I'd rule out the computer and the crank sensor for now. Based on what you wrote, I'd rule out the coil pack harnesses, since the engine ran smoothly.
Have you inspected the coil packs for hairline cracks?
Do both power stages have battery voltage at pin #4?
A regular test light will not be sufficient to test for control at the coil pack.
Perhaps try pulling a plug again, but this time ground the coil pack through its bolt hole.

danr960 · Post by **danr960** » 14 Jul 2014, 07:37

I had this happen too, for me it turned out that the ground for the power stages was not connected. My 94 has a ground tang that is located on the driver side engine mount bracket. There is a black plastic wire chase that hold some harness wires, the 10mm bolt that hold this plastic piece also holds the ground tang. It was missed on disassembly and caused a few hours of trouble shooting to find. Hope this is your problem.

DanR

dougsbart · Post by **dougsbart** » 16 Jul 2014, 16:16

I have been traveling for a few days. I will chase down these suggestions and report back. One point of clarification what "both power stages" and which is pin #4?
thanks

Ethan Rode · Post by **Ethan Rode** » 19 Jul 2014, 23:14

There are two ignition power stages on either side of the intake manifold, the pins in the connectors will be numbered.

dougsbart · Post by **dougsbart** » 09 Sep 2014, 09:44

Thanks all! Dan was correct! bad ground on drivers side by mount, hard to see under intake etc. I appreciate the replies and I hope this thread helps others chasing a ghost.