Thread: 3.5 Carby V8 hard to start when hot

Originally Posted by Blknight.aus

you might have a problem with the dual fuel control and its trying to run both fuels at once flooding it out completely. areostart wont help you then.

LPG not connected at the moment as it needs a new converter. So I think I will set it up for normal unleaded at the moment and when the new converter is in the LPG man can tune it to run on both fuels - just want to to run at the moment.

Garry

Originally Posted by garrycol

LPG not connected at the moment as it needs a new converter. So I think I will set it up for normal unleaded at the moment and when the new converter is in the LPG man can tune it to run on both fuels - just want to to run at the moment.

Garry

Oh, you set your timing on the road on fuel as LPG can handle alot more advance, than LPG, put Premium in, don't be a tight ass, that way you can run more timing prior to ping

Engine started again perfectly this morning but gets harder to start as the engine gets hotter. I will see what happens with new plugs etc.

Garry

Garry, does this engine have good compression? And did you say the spark is OK?

The reason I am asking about compression is that the amount of vacuum available to lift the carb slides during cranking is reduced dramatically with worn valves/ rings etc, therefore making it difficult to get adequate fuel/ air for ignition. Cold starts are slightly different because the choke dumps extra fuel in rather than choking off air like other 'lesser' carbs.(I have seen a early flapper type EFI 3.5 have such low compression that it barely opened the flap during cranking enough to trip the fuel pump contacts)

Anyway, just a thought....

JC

Originally Posted by justinc

Garry, does this engine have good compression? And did you say the spark is OK?

The reason I am asking about compression is that the amount of vacuum available to lift the carb slides during cranking is reduced dramatically with worn valves/ rings etc, therefore making it difficult to get adequate fuel/ air for ignition. Cold starts are slightly different because the choke dumps extra fuel in rather than choking off air like other 'lesser' carbs.(I have seen a early flapper type EFI 3.5 have such low compression that it barely opened the flap during cranking enough to trip the fuel pump contacts)

Anyway, just a thought....

JC

I have no reason to doubt the level of compression - the engine pulls Ok and performance is what it should be however when I replace the plugs during the week I will do a compression test to double check. To ensure the LPG mixer was not strangling the engine (it does have a small orifice) I have taken it off while testing so the carbies are getting a full dose of air - also replaced the carby diaphragms as a precaution. The point I need to check is whether I am sucking in air somewhere but nothing is obvious.

I have only tried No 1 cylinder spark at this stage as it is too hard to test the HT lead with waterproofing gear on it. The spark is strong (I got zapped) but when cranking, the spark is not always regular - as well there is considerable spark on the points so the condenser may have failed.

So I will do the easy things first like new plugs, points and condenser and go from there.

Cheers

Garry

Originally Posted by garrycol

I have no reason to doubt the level of compression - the engine pulls Ok and performance is what it should be however when I replace the plugs during the week I will do a compression test to double check. To ensure the LPG mixer was not strangling the engine (it does have a small orifice) I have taken it off while testing so the carbies are getting a full dose of air - also replaced the carby diaphragms as a precaution. The point I need to check is whether I am sucking in air somewhere but nothing is obvious.

I have only tried No 1 cylinder spark at this stage as it is too hard to test the HT lead with waterproofing gear on it. The spark is strong (I got zapped) but when cranking, the spark is not always regular - as well there is considerable spark on the points so the condenser may have failed.
So I will do the easy things first like new plugs, points and condenser and go from there.

Cheers

Garry

That is a very definate possibilty Garry.

JC

Another possibility is the coil. I have had a few vehicles that at various times the coil broke down as it got hot. The motor would cough and splutter a bit as well.

have seen rotor buttons do what is happening to yours..

my first v8 disco did a similar thing and it drove me nuts for two days till i swapped the rotor and away it went.

there was no visible fault on the one that was playing up and when not under load it worked just fine.. bit of heat and load and it died...