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Discussion Starter · #1 ·
Thought I had my hard start and random stall issue figured out, but nope.


Fuel pressure is good! Confirmed multiple times testing. 39-42 psi with ignition on.

Intermittent no spark from coil. Usually if I let us sit then try in morning I get nothing. After cranking forever and messing around checking voltages etc all of a sudden I get perfect spark.

PO did remote amp install and Mallory dizzy.

Replaced coil and amp module.

Referring to this test I get voltage between pos battery to neg coil with ign off and on. About 11-12

Will fore up no issues after messing around with it for a little while. Come back next morning and no start, will start again after messing around for a little while. I replaced all grounds and checked all connections. Distributor ohms are within spec.


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1985 RRC 3.5, LT230, LT77. 1996 Disco1, 4.0
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Switched my '85 (carb engine) over to OEM module dizzy. Ran amp over to left front fender as it wouldn't clear the PS pump. If the lead from coil to dizzy was anywhere near the remote amp wiring, there would be no spark. Fabbed the amp harness, it's not shielded. Moving the coil lead was a "free" fix vs buying a location kit.

As yours is aftermarket, my issue might not relate to your issue at hand. Sharing cause symptoms you're describing are close to what I experienced...took 4 days to find it! All tests checked good, even purchased a new module thinking I had fried the 1st one...

I also had to ground the dizzy and the module...
 

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Adding to above, remember that coil load switching is the earth line to saturate (connected) and fire (disconnect) the coil, needing routing earth line to function reliably.
 

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Discussion Starter · #4 ·
So all more testing I’ve carried out points to a faulty Mallory unilite module. New one on order.


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Discussion Starter · #5 ·
Replaced module, starts and runs but now surging idle, more present at start up .


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Sounds like progress at least to have it running again.

Surging I'd look at air leaks initially as any uncontrolled air into the intake causes inaccuracies in ECU response via IACV.

Quick check for IACV functionality, after switching off unplug IACV from loom multi pin plug, then start it again. It should go straight to about 2750rpm idle which confirms that the IACV is using it's whole range. It sets it wide open at switch off to facilitate the next start with a high idle speed to give it air while cranking.
If that checks out, switch off and plug it in again, then start and it should be back to normal.
 

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To add further thought, have you verified the timing is on target as significant discrepancy can give surge characteristics with the ECU logic IACV steps not matching redponse to give over and under run rpm modulation.

You could also disconnect the IACV air pipe and plug both ends as a way to diagnosis. Still surging, it's not the control. No surge, and it means you are definitely looking at the control circuit for error.
 

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Discussion Starter · #8 ·
To add further thought, have you verified the timing is on target as significant discrepancy can give surge characteristics with the ECU logic IACV steps not matching redponse to give over and under run rpm modulation.

You could also disconnect the IACV air pipe and plug both ends as a way to diagnosis. Still surging, it's not the control. No surge, and it means you are definitely looking at the control circuit for error.
Thank you sir.

I ended up replacing the amplifier module and that ironically took care of the problem.


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