Starting issues sometimes lately

[webbew]

Hi all,

after years of completely trouble-free motoring, lately when I start, it sometimes doesn't behave as usual. Here's what's happening normally: When I turn the key, there's a "clack" noise (sounds like a relay), then you can hear a faint sucking noise for about 2-3 seconds and then another "clack". Then I turn the key fully to crank and the engine starts rightaway. When the car has been sitting for a while, doing the clack-clack 2-3 times before cranking seems necessary sometimes, that's fine.

Over the past couple of weeks I have noticed a handful of times that there is only 1 clack and no second one, or the 2 clacks are immediately after each other. I have learned by now that in this case there's no point trying to crank the engine, it just won't start, so I try again and at some point I get the "normal" clack-2s wait-clack and then it starts fine.

As you can probably tell from my description, I'm not exactly a full-on greasemonkey - any suggestions appreciated, I'll probably take it to the mechanic anyway, but always like to learn/know a bit about what's going on anyway!

Thanks!

[Steptoe]

OK lets get this clear...
you turn the key to start the cark and get a 'clan" ans sometimes it take a couple attemps for the engine to turn over???

This is a symptom of
1/A battery dieing
2/loose or dirty battery terminals and/ or the terminals oin the starter
Above is most common

3/ The starter solnoid contact needs replacing
4/Worn bushes, bruches bearings in the starter
5/The armiture is getting dry solder joints due to intail timing being to far advanced over a long period.
Above replace starter

6 Alternater is not giving full charge.

[webbew]

Thanks, sorry I probably didn't explain right. Cranking/starting is totally fine. The "clack - faint sucking noise for 2-3 seconds - another clack" is when I turn the key to the ACC position (I think that's what it's called), i.e. before I crank it. When I turn the key to the last position (i.e. start), it starts pretty much immediately - provided the 2 "clack"-noises were properly 2-3 seconds apart.

Sometimes lately, there is either only 1 "clack" noise (even if I wait say 10 seconds with the key on ACC), and sometimes the 2 "clack" noises are immediately after each other (all while the key is just on ACC). If I would then try to start the car by turning the key to the start position, I found it's pointless, it'll just crank but not fire.

As far as I understand, the "clack" is the relay of the primer, the faint sucking noise the priming with LPG. It makes sense to me that if the engine isn't primed with the right amount of LPG, it won't start (since the valves on the LPG line won't open unless the engine is running), right? So, just want to confirm my understanding. If that is so, I guess my next question would be is there anything servicable or something that needs cleaning on the primer?

[Steptoe]

Have to turn this over to one of the other guys...
I have never used a primer....just turn the engine over and as the oil light goes out the engine fires.
Never worked aout the relationship between them , but thats wha happens....colder the engine the longer it takes for oil pressure to come up.

[C3H8]

A little more info would help. Make and type of vehicle and name of LPG system. What you are describing is the priming system of units similar to Vialle or some Italian makes. The clack is the primer solenoid. The sucking sound is actually gas flowing into the propane hose and then into the intake to prime the engine for starting. The second clack is the solenoid closing because you haven't cranked the engine yet. Cycling the key does it again. The operation of the solenoids is controlled by a computer type module that allows a 2 second prime. If the engine is not cranked the module turns the power off to the solenoid. Either the module has failed, or the solenoid coil is going bad, or the solenoid plunger is sticking. I opt for the stuck plunger at this point from your description. The heavy ends and/or powder found in propane has probably migrated to the top of the plunger in the primer solenoid and the plunger is sticking so you don't get any prime. In addition this solenoid must be open to allow the engine to run continuously one you try to start it. Check the brand name on the reg and one of us might be able to tell you where to check.

[webbew]

It's been over 2 months now and I have never had the issue of the primer not priming properly again (as described earlier) so far, but I have finally gotten around to taking some pictures.
My car is a '73 Chevy Impala wagon, 400 sb with Edelbrock Performer heads & intake manifold and Technocarb mixer from TorqueGas. The converter says LONGAS AIROD CLASS1/2A and "Made in Italy" on it.

There's also a mystery box - presumably the computer type module that C3H8 mentioned.

Sorry I don't know more about all this - I'm not a mechanic, I just enjoy the end result
...and to put things in perspective, I've been *very* happy with my Chevy for the past 5 years since all this has been done - no issues with power, economy, reliability, no maintenance whatsoever needed so far, always starts/runs fine, apart from like I said every once in a blue moon the primer doesn't prime right-away and it takes me a few attempts to get the solenoid clacking properly and then everything's fine.

[webbew]

PS: Just out of curiosity - is the vaporizer appropriate for the mixer & engine; or to rephrase: would it be worthwhile having 2 vaporizers? (the mixer is fed by 2 hoses, with a Y coming from the one mixer, as you can see in the engine bay picture below).

[webbew]

Is the primer is what you can see directly mounted to the left of the converter? (2nd picture further above) If so, it says "TYPE 07-LPG-MAX W.P.3 MPa AGA 5135" (see writing on the brass part in 2nd picture above). The leaflet that came with it says it's an "Airod Series 07 Direct mount Gas Solenoid".

Or is it the black pastic box on the converter? - see picture below

Any advice on what to look for/how to clean it?

Thanks!

[C3H8]

I've seen a lot of different equipment in Canada but never this brand. I can't help ypu here. Maybe one of the others.

[webbew]

fwiw, I got it all from TorqueGas in Australia

Update: Figured out the black plastic box under the converter is the primer. It has a screw on it for what I think is for adjusting the mixture (lean/rich) for priming (i.e. how much fuel it uses for priming). It seems the rectangular box mounted on the firewall is the timer (also has a screw for adjusting how long each prime lasts).

[webbew]

...an update on this old post of mine, in case anyone's interested:

Turns out the box mounted on the firewall is supplying voltage to the solenoid in front of the vaporizer as follows: when the ignition key is turned, it opens the solenoid to allow for priming (first clicking sound). You could crank the engine at that stage, and if recently driven, it would fire up. If you do nothing, an adjustable timer in that box closes the solenoid again after 1-2 seconds (second clicking sound), presumably also for safety.
Whenever I haven't driven in a while, I prime twice, so I listen out for the 2nd clicking sound to know when it's finished priming.

The box also has another cable going into it that feeds off the ignition signal, so that once the engine is running, it keeps the solenoid open, but if the engine would stop, it would close it (again, for safety). So, on a cold start, if I prime twice and then crank the engine, there's enough LPG there to start the engine, and once started, the box gets the ignition signal to keep the solenoid open. Interestingly, if I crank after the solenoid actually closed again, it doesn't matter either, it happily re-opens the solenoid quickly enough (once it gets the ignition signal from the now running engine) to keep the engine running.

To cut a long story short, that box/timer had an intermittent fault, which happened quite rarely, making it hard to explain to/diagnose by my local LPG guy. However, luckily(?), we managed to reproduce it and he immediately suggested to replace that box (only about $80). Replaced it, now it seems all good again, yay!