BrynT Posted June 15, 2020 Share Posted June 15, 2020 Drove my V8 3.9 EFi Defender less than one mile last weekend to pick up animal feed, parked up, left it for a day then it wouldn’t start. I get no spark. I’m trying to diagnose the source of no spark and have tested resistance of the Magnecor HT leads, it’s got brand new plugs about 750-1000 miles ago so I’m hoping / doubting that’s not an issue (I’m open to hear more wisdom though). I’ve tested for spark from the coil to distributor and get nothing, so the coil is the next thing to check. I’m getting roughly battery voltage from both coil terminals to earth. Does anyone know the primary and secondary resistance of a Bosch PRC6574 ignition coil? Any other suggestions (tbh the wiring is a bit of a shambles so it could easily have been me knocking a wire or something when I was rummaging in the engine bay for the engine serial number). Any suggestions gratefully received. Quote Link to comment Share on other sites More sharing options...
Bigj66 Posted June 15, 2020 Share Posted June 15, 2020 Do you have an ignition amplifier fitted to the distributor? A failure of that will cause a loss of spark. Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 16, 2020 Author Share Posted June 16, 2020 Thanks for that. Is there a way of testing the ignition amplifier? Quote Link to comment Share on other sites More sharing options...
Bigj66 Posted June 16, 2020 Share Posted June 16, 2020 6 hours ago, BrynT said: Thanks for that. Is there a way of testing the ignition amplifier? There probably is and hopefully someone on here can explain what the procedure is as I seem to recall just swapping mine with a known good one to diagnose the fault. It was many moons ago though but if it is the amplifier then consider changing it to an aftermarket one that’s more reliable and less prone to failure. Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 16, 2020 Author Share Posted June 16, 2020 I checked and pretty sure there is no amplifier present. From what I've seen in Haynes and online it's a small device that I think should be connected close to the coil, and there is nothing like that. Do you know how it connects to the coil? If the terminal, which one? Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 16, 2020 Author Share Posted June 16, 2020 BTW - Haynes Discovery 1 1989-1998 (I think the engine came from one) states the following. My primary is 0.8 ohms, secondary 9K ohms. Given what Haynes states it sounds high but I though Bosch range was higher, but I do not have anything definitive stating that fact. A dumb question perhaps, would a higher resistance indicate it has failed? Quote Link to comment Share on other sites More sharing options...
Bigj66 Posted June 16, 2020 Share Posted June 16, 2020 If you have one it will be fixed to the side of the distributor. 1 Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted June 16, 2020 Share Posted June 16, 2020 Or it could be a metal box that the coil is bolted to. It's the #1 cause of V8 ignition issues. 1 Quote Link to comment Share on other sites More sharing options...
300tditaffy Posted June 16, 2020 Share Posted June 16, 2020 I had a rotor arm go down to earth which caused the same problem you have, it was running fine and then it went with no warning 1 Quote Link to comment Share on other sites More sharing options...
Bigj66 Posted June 16, 2020 Share Posted June 16, 2020 1 hour ago, 300tditaffy said: I had a rotor arm go down to earth which caused the same problem you have, it was running fine and then it went with no warning I’ve had this too. Rotor will look fine but it shorts out internally. Substitute with a known good one. Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 17, 2020 Author Share Posted June 17, 2020 Thanks everyone. I've found the Ignition Amplifier (attached to the Distributor) so that's the next step. They're so cheap I'm just going to replace it rather than test. It sounds like a sensible thing to do regardless. Would folks recommend repositioning next to the coil at the same time - is there any advantage (heat/vibration) to have elsewhere? Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 17, 2020 Author Share Posted June 17, 2020 Interestingly enough I found a new rotor arm in the battery compartment (in original packaging) so a previous owner has clearly encountered this. Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 17, 2020 Author Share Posted June 17, 2020 BTW - I found this about testing the Ignition Amplifier. It seems to be a well quoted site. http://www.vintagemodelairplane.com/pages/Ignition/AmplifierTest01.html Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted June 17, 2020 Share Posted June 17, 2020 5 hours ago, BrynT said: Thanks everyone. I've found the Ignition Amplifier (attached to the Distributor) so that's the next step. They're so cheap I'm just going to replace it rather than test. It sounds like a sensible thing to do regardless. Would folks recommend repositioning next to the coil at the same time - is there any advantage (heat/vibration) to have elsewhere? Not sure I'd go to the bother, it's the sort of component I'd be inclined to just carry a spare one of in the glove box I did replace the early type (box under the coil) with a GM part on my RRC, there was a guide on the V8 Capri site about it, worked nicely. 1 Quote Link to comment Share on other sites More sharing options...
BrynT Posted June 21, 2020 Author Share Posted June 21, 2020 Many thanks to all that have offered advice. You were all very helpful. The engine is running nicely now and it was all down to a faulty wire between the Ignition Amplifier and Coil. I've ordered a new ignition amplified on the basis that my toolbox should have one, just in case. In addition I fitted a new V fan belt to solve a horrible squealing, replacing the incorrect spec belt that came with the vehicle (13mm, not 10mm which was sat deep in the pulley and could be slipped over them by hand). It sounds great now, except... ...I have 1 more favour to ask. I'm pretty sure I have a stepper motor issue. Idle speed is high, and after a clean with carburettor cleaner I was getting improvement, although intermittently. I'm convinced the stepper motor is failing it's job and I believe there are two types listed as replacements. Unfortunately they are referenced according to the vehicle, not the engine serial number, so I'm a bit buggered figuring out which one I need, as follows: ETC6660 used in Discovery 1 V8EFI to VIN MA112200 & RRC V8EFI to VIN MA656101 ERR5199 used in Discovery 1 V8EFI from VIN MA112201 & RRC V8EFI from VIN MA656102 My questions Is there another way of working out which I need? Is there a way to figure out from the engine serial number, to which vehicle it might have been fitted? I think if I replace the stepper motor I have to reset the ECU. Lacking any technical kit, would I be best getting the local garage to configure the reset? Appreciate any further help / advice you have. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted June 21, 2020 Share Posted June 21, 2020 You shouldn't need to go to a garage to reset it, I have a feeling just disconnecting the battery for a while does it but I'm sure there's details in the RAVE manual and/or someone will be along shortly to tell you how. 1 Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 21, 2020 Share Posted June 21, 2020 Yes, it just self-learns again, just swap it out and it will work itself out after half a dozen drives or so. 2 Quote Link to comment Share on other sites More sharing options...
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