Update on changes to LPG on 4.6 P38

[ytt105]

The story so far....
1996 P38 4.6 V8. Fitted with LPG before I bought it. The system was an IMPCO 425 inline 'gas carby'.
It performed OK, no problems, BUT died in the bum when towing or going up hills. Given the stick unladen and it went well, but no torque.

So Bee Utey to the rescue.

It now has the M352 gas ring with a Zavoli convertor, dont get me started on my waste of money with a 2nd hand OMVL, and an O2 computer controled adjustable power valve.

Just got the mixtures adjusted by the local 'gas expert'. It goes quite well, haven't tested it towing yet, but it has a flat spot just as you take off. The 'expert' said I may need to open up the power valve a bit more to get rid of it. I've done that and it has stopped the flat spot, but now it smells of gas when it is stopped. Can't find any leaks and can't smell anything when its running.

Have I opened it to far? How do you adjust the power valve, and the Zavolli for that matter?

PS. The 'expert' said if it doesn't work properly, the computer controlled power valve should be replaced with a standard power valve!!

[bee utey]

The "expert" who adjuts the mixtures should be you, not some disinterested third party. All adjustments are easy, the LPG computer readout lights will be a great help. I won't be back in until tonight, can help you over the phone then. PM me your mobile so I can advise. It takes longer to describe the operation than it actually takes to do it.

[ytt105]

Thanks for that Jilden. I'm away till Tuesday so will ring you then. I just towed a lightly laden trailer and actually passed a Toyota up a hill. First time ever. So very happy so far. Thanks again.

[ytt105]

A further update.

Thanks for the offer of phone help Jilden, but before I rang you I thought it would be a good idea to check my wiring.

What I found was that the TPS was wired incorrectly. The yellow/green wire was the one that carried the voltage signal, not the red one.

So I rewired and then followed the instructions from the Gastec site (http://storage.fiat-bg.org/Gazovi_uredbi/fp30insA.pdf) and it runs great now. All the lights do as there supposed to and as you say it was quite easy.

The only thing I haven't touched, or understand for that matter, is the mixture control on the Zavoli. How can I adjust that? Are there any lights to help with it?

As ever Jilden you have been incredibly helpful and a right on the money with your advice.

[bee utey]

There are two adjustments on the Zavoli. Unless your gas man fiddled with it, the recessed brass screw in the top of the converter should be left alone. It should be about 2-3mm below flush.

The main idle mixture adjustment is done with the knurled brass knob sticking out of the face. With the engine warm and idling, screw this knob in until the engine slows down and the computer box shows the "lean" light on. Then turn out the knob until the rich light comes back on, and the idle becomes smooth. When you crack open the throttle a bit the idle speed should rise smoothly without the "lean" light coming on. A bit more mixture on the knurled knob may achieve this if necessary. If you can't get it to rise smoothly from idle without leaning off, screw in the recessed adjuster by 1/2 a turn and do the procedure again. While you are adjusting the idle the idle light on the computer should be on and the stepper unplugged.

When the idle and just off idle are smooth, snap open the throttle and see that the "rich" light remains on. If all goes well plug the stepper back in, raise the engine speed and watch for the lean-rich-lean showing the stepper is working.

[ytt105]

It goes real well now The only issues left are slight smell of gas when the engine is switched off and it is difficult to start after the first start. I think the starting problem has to do with the old petrol/gas start control thing. So I think I will remove it and wire up the start control in the new computer

[bee utey]

It goes real well now The only issues left are slight smell of gas when the engine is switched off and it is difficult to start after the first start. I think the starting problem has to do with the old petrol/gas start control thing. So I think I will remove it and wire up the start control in the new computer

LPG flooding is a normal problem on cold restarts. Nothing you can do other than to run the engine a minimum of 5 minutes after a cold start. Wiring the injector cuts through the computer makes for a much more robust system. However with only a single relay you need to have the injector cuts in the positive wiring to the injectors, and possibly rewire the positive to the MAF. It depends where your old injector cut relay was fitted.