Thread: Backfire Protector Valves (and a couple of other questions)

Originally Posted by geodon

OK, in the interest of avoiding a chk-chk-BOOM scenario:

1: The high pressure liquid feed from the tank.

2. A cut-off solenoid

3. The Gas feed to the mixer

4& 5 hot water from cooling system.

So if I unhook the hose @3 & press the springloaded button in the middle of the converter, I should get a gas supply at the spigot 3?

Don't I have to energise that solenoid? I mean there can't be gas coming out with just the ingnition switched on. Isn't there a safety circuit that detects the engine turning over eg running or cranking to start? Otherwise, if the engine stalls & (or an accident occurs) and the ign is left on that would mean the engine bay fills with gas. chk-chk-BOOM??

Basically correct but I told you (in the post below) the order of events which will energise the solenoid. It will open for around 1 second when you turn on the ignition and gas switches. In some installations you might have to energise the starter for a moment.

If the converter is stuffed you are safely away from the converter and can switch it off pronto. If the converter and electrics work as advertised you will then have some gas trapped in the converter which will be released on pressing said button.

PS I do have some spare Impco bits if you find yours are faulty.

Well now it won't run on petrol again despite a successful 10km test yesterday run after cleaning the MAF sensor wires. So the MAF unit must have been in its death throes or have an intermittent fault? Is this what they do when they play up?

I can get one in the states for $US332 + an extortionate amount for the pirates at UPS!

Maf - Auto Parts Warehouse=

Local source?

Can anyone loan me a serviceable unit for a diagnostic check before I invest in one? I'm in the Melbourne CBD or Geelong or I'm prepared to pay postage both ways & there's a decent bottle of McLaren Vale shiraz in it for you. PM me your email.

Check for spark, fuel pump etc as the engine will run with a faulty/disconnected MAF as you found out. If spark is present the gas should be easy to get going. You should probably adjust the plug gap to 0.7mm before you try the gas again, it reduces the chance of backfiring.

BTW Bee Utey, mate you were dead on re the Impco Mixer! 1st Order Low Technology. Just a spring loaded diaphragm (VERY intact I might add!) that lets in more gas as more air flows thru and compresses the spring.

I checked the converter: ign on & press the button gives me ONE puff of gas so there MUST be an aditional circuit that detects the engine turning or cranking before letting gas thru.

BUT what is different this time is it's JUST as bad with the MAF disconnected, ergo something is "stuck" in one setting. Check this ref under "Cold Stall".

Range Rover Remedies

OR do I need to reset the ECM??

There are 5 male pins on the MAF & 4 female connectors on the plug. I have a Multi-Meter. Can I test it? Isn't there a "Faults" display thingy somewhere? My Rave1 CD is in the mail.

The most common problem I used to meet with D1/RRC dual fuel engines was the partial or complete failure of the ignition amplifier. I developed a cheap repair method, shown in this thread:

Lucas ignition amplifier replacement by Bosch 024

From your link:

The ignition amplifier module is a notorious cause of hot stalling and stuttering. Dean Sonneborn found the heat buildup under the hood when his 1990 RR was not moving (eg stopped at traffic lights) caused his ignition amplifier module to fail intermittently, stalling the engine. The faulty unit was so sensitive to temperature that even a minute or two of cooler air provided by opening the hood got it working again.

Check the ignition is working AOK first and foremost.

The gas system uses a connection from the negative side of the ignition coil to determine whether the engine is running and needs gas. No spark = no gas flow (after the 1 second first on-period).

AFAIK you don't need to do anything to the ECU. It's pretty stupid and works when everything is plugged in and correct.

Well that's food for thought- the ign system may have failed as I changed from petrol to gas coincidentally.

Where is the OEM ign amp on my '92 RRC? It's not near the coil.

I unhooked the HT lead for the top of the cap & got a steady stream of fat sparks anything up to 12mm from an earth as the eng cranked which may not mean much!

I got it to run on petrol (reasonably well too) for a while with the FAM unhooked but I could not reproduce it despite trying repeatedly.

I guess that's what an intermittent fault is about!

BTW, I run a Bosch dist on my MGA.

Huns 1 (heading for 2?), Prince of Darkness 0.

Originally Posted by geodon

Where is the OEM ign amp on my '92 RRC? It's not near the coil.

It's where the wires in my conversion connect to the dissy. Remove amp, connect wires, fit amp&coil away from the heat.

Originally Posted by geodon

I unhooked the HT lead for the top of the cap & got a steady stream of fat sparks anything up to 12mm from an earth as the eng cranked which may not mean much!

Try this again with the dissy cap off, aim the lead at the centre of the rotor button. If spark jumps to the brass strip in any significant way your rotor button could be fried. You can use a XF Falcon rotor instead of aftermarket cheapie RR replacement. It's Bosch part no. GB864, works the same but looks quite different.

These don't look real healthy to me!

The end of the rotor is SINTERED and so are the terminals inside the cap.

Bee Utey, I assume that is the OEM Ign Amp under the black connector?

Well I will try a replacement rotor & cap and see what happens. Can't quite see how they could fail so suddenly but their condition warrants replacement anyway.

So a new Lucas cap & a Bosch GB 864 rotor is the go? Or is there a good aftermarket cap as well?