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TOPIC: hard to start

hard to start 14 Jun 2017 08:31 #19791


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I have an 87 928 with 264K miles on it...runs perfect..but on 2 occasions recently I have had a problem starting it after a short drive when it sat for 30-45 minutes..the first occurrence was about 6 wks ago & it cranked over fine, but never fired once...I let it sit & retrieved the car later in the day..it started on the first crank...yesterday morning the same thing occurred & it finally started after about 12-15 tries with short intervals between tries...when it finally started...it ran perfectly again...It never once fired during all the cranking...until all sudden started as normal....anyone have a suggestion as to what I should look at????
Thanks!!!!
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hard to start 15 Jun 2017 15:12 #19798


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Hello TBT,

It helps to know if the cause of no-start is no spark. If so, there is a very good diagnosis trail in factory workshop manual.;

Hard start problems have many possible causes. Start with the easy stuff:
- inspect and clean all chassis ground points (anywhere a brown wire is screwed into the chassis). Also clean the cable that goes from the engine to the chassis.
- inspect and clean all connectors, pay attention to the battery cables where the positive cable has additional connections and the negative where it connects to the battery and chassis. The negative cable is covered with plastic and if there is corrosion, it can corrode under the plastic sight unseen.
- replace the LH, EZK and Fuel pump relays (very common cause of no-start)

If the problem continues, the next thing to check is the Temp II sensor. They sometimes fail in a way that causes no start, though a more common problem is cold start if they're out of spec. Given the miles on the car, it can't hurt to replace it.

Does the fuel pump make a loud noise? If the pump is getting hot it may need to cool down.

It could be that the LH fuel injection module is on the way to failing. The 1987 and newer 928 LH fuel injection modules have a fairly high failure rate due to a hybrid circuit. It is difficult to diagnose 100% unless the module completely fails.

Good luck,
Rich
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1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast
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hard to start 15 Jun 2017 15:52 #19799


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Another possible reason is a failure of the crank position sensor (CPS). I had this happen to me with my '90. The car would fail to start once or a few times, then start and run fine (see my post on this: 928oc.org/forum/928-oc-member-car-profil...0-s4?start=160#18986). The frequency of no-starts increased rapidly. A signal from the CPS is required to trigger the LH, which then triggers to EZK. So without a good signal there is no spark.
Last Edit: 15 Jun 2017 15:53 by martinss.
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