RWD - Cranking No-Start; Diagnosis on 940 Turbo

Volvo RWD 900 Forum

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Cranking No-Start; Diagnosis on 940 Turbo 900

Hey all,

After a few short trips during the day, on a final errand the car was running fine for about a mile after a warm start when the engine completely died and all panel lights came on. It restarted and ran for another 15 seconds or so, enough time to get it out of traffic. Subsequently it was towed into my driveway.

Following the typical script, here's where I am at:
- Fuel pump relay clicks closed and allows main pump to audibly "prime" when ignition is turned ON
- Fuel pump seems to run during cranking, and I hear the relay click open a couple of seconds after stopping cranking per usual. So Hall sensor seems good.
- Visual confirmation: Crankshaft is turning while cranking, so timing belt is good.
- No trouble codes stored in ODB; basic ODB tests "pass"
- Power stage connector is clean and proper.
- Spark plug wire pulled from plug and held close to engine block delivers spark; not sure how much spark to look for, but to me it seems a little weak
- With ignition coil connections removed and fully cleaned, coil delivers 11v at ON (between T15 and ground as well as T1 and ground). Is the fact that it's one shy of 12v enough to prevent starting?
- Resistance test of coil shows 1.3 ohms for primary (vs. the .6 to .9 range specified in the FAQ. Is the fact I'm over by .4 to .7 enough to prevent starting?) Resistance of secondary is 7.6K ohms (within the 7.0 to 8.5k range stated in the FAQ).

What do you think; is the coil marginal and keeping the ignition from starting? If so I can swap it. Or do you think it's probably "good enough" and I should move on to troubleshooting the FP relay contacts and pumps themselves?

Thanks for your thoughts.


New Cranking No-Start; Diagnosis on 940 Turbo [900]
posted by  Greg R  on Sat Oct 5 15:04 CST 2019 >

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