Thread: Trouble starting engine on 1988 3.5 on LPG

Originally Posted by TABBIT

I have a 1988 3.5 Range Rover that I have owned since 1997, I had it put on LPG back then, and it has always started perfectly, until about 7 months ago, when one morning it refused to start, since then it has been only a prayer that gets it going, I have replaced, the distributer, the rotor button the leads the spark plugs, upgraded to amore powerful coil ran a power relay directly to the coil, the battery is a 575 starting amp one and measures 570, I had the impco gas system checked and replaced the converter , I am now trying to get the petrol side going which neglected for the past 5 years I have replaced the perished hoses to the injectors, only to reveal some blocked injectors which I will replace next weekend, Sometimes when it does start it is that nano second when the key is released and the load of the starter is taken away, my mechanic says this doesn't matter, I'm wondering about the temperature sensing switch that allows a spray of petrol into the plennum, but apart from that I have ran out of ideas. I am hoping someone out there has some new ideas.

Most EFI systems rely on a small amount of petrol injection to get the car started easily. If your petrol system has failed I would start by fixing that.

It is possible to fit a manual primer to your Impco system, you would need a solenoid connected to the pressure port on the converter, and plumb this to the inlet manifold. The primer should have its own press button from the ignition or gas switch. My old rangie never starts without a 2 second prime.

I assume you have checked for spark while cranking. It should always have a strong spark at any plug lead. Use an old spark plug with the gap opened to 6mm to check, securely earthed. You may have a worn ignition switch.

Thanks bee utey, I have a primer fitted it gives about a moment of engine run then goes back to cranking, spark, last time I checked was good, and the plennum petrol primer was working last time, thanks again.

Originally Posted by TABBIT

Thanks bee utey, I have a primer fitted it gives about a moment of engine run then goes back to cranking, spark, last time I checked was good, and the plennum petrol primer was working last time, thanks again.

In that case I suspect flooding. Disconnect the petrol start and use the primer only. Some Impco systems start better if you operate the primer after you start cranking. It also sometimes helps to give it a little throttle AFTER you have started cranking. About 1 inch on the pedal is enough, more may lead to a backfire!

Thanks, I will give that a try, what about low compression? this was suggested to me today. I was going to check that tomorrow.

Originally Posted by TABBIT

Thanks, I will give that a try, what about low compression? this was suggested to me today. I was going to check that tomorrow.

Could be but you would notice power loss? To be honest my RR starts much easier since it got a better starter motor and battery. The original Lucas starter was not too good and it turns much better with the Bosch starter and N70Z battery. Always starts first pop every time now. I got a used Bosch starter from the local landy wrecker, came out of a Disco series 1.

Thanks again bee utey, I have a new Bosch starter motor in it, even though the battery is good I am thinking of upgrading it from a 575 to a 700, I know that this won't fix the problem, but it will give me more cranking time. In the meantime I am getting the gas checked tomorrow as it has backfired a few times when the engine is under load, I'm told this is a sign that it is too lean, maybe this has an impact on starting.

Originally Posted by TABBIT

Thanks again bee utey, I have a new Bosch starter motor in it, even though the battery is good I am thinking of upgrading it from a 575 to a 700, I know that this won't fix the problem, but it will give me more cranking time. In the meantime I am getting the gas checked tomorrow as it has backfired a few times when the engine is under load, I'm told this is a sign that it is too lean, maybe this has an impact on starting.

And that brings me to the last reason for hard starting, spark plug choice. My favourite gas plug is Bosch part no. WR7DC+ but you can use NGK BPR6ES if you prefer jap stuff. Make sure the gap is no more than 0.7mm/0.028" and it should handle lean mixtures better. Bosch also make a LPG specific platinum plug, part no. WR7KI33S, pre-gapped for lpg to 0.7mm.

Also make sure your plug leads are not tied together, a bit of space between them is good backfire protection.

what about for a 4.6 on lpg?? This afternoon she was rough as & power loss between 2 ~ 3,00rpm time to rip the sparks & replace so I am wondering what is best to use??