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Coughs but won't run!


paul mc
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After fitting new head gaskets and timing chain I can't get the engine to run again. Every time i turn the key the engine very briefly fires up then cuts out straight away.

I am thinking its a timing problem but using a timing light at least shows the timing is perfect, No1 is firing at exactly TDC, although i have turned the dizzy both directions to check if slight advance or retard helps to no avail.

I'm thinking the timing is out from fitting the new chain and sprockets but i thought i followed the Haynes manual to the letter, but this is the first time i've ever done it before. Obviously the marks on the sprockets lined up but maybe the camshaft was not correctly orientated to the crankshaft, i.e. one or other was a revolution out or something similar. Before i take the timing cover off again this weekend abd start again is there anything i need to look out for? Any tips for a timing newbee?

Or maybe it isn't timing at all? All plugs are sparking and don't think its fuel related as the engine won't start on 'easy start' and when i took the plugs out i could smell petrol.

Any help much appreciated

1987 RRC 3.5 V8 EFi

Cheers, Paul

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After fitting new head gaskets and timing chain I can't get the engine to run again. Every time i turn the key the engine very briefly fires up then cuts out straight away.

I am thinking its a timing problem but using a timing light at least shows the timing is perfect, No1 is firing at exactly TDC, although i have turned the dizzy both directions to check if slight advance or retard helps to no avail.

I'm thinking the timing is out from fitting the new chain and sprockets but i thought i followed the Haynes manual to the letter, but this is the first time i've ever done it before. Obviously the marks on the sprockets lined up but maybe the camshaft was not correctly orientated to the crankshaft, i.e. one or other was a revolution out or something similar. Before i take the timing cover off again this weekend abd start again is there anything i need to look out for? Any tips for a timing newbee?

Or maybe it isn't timing at all? All plugs are sparking and don't think its fuel related as the engine won't start on 'easy start' and when i took the plugs out i could smell petrol.

Any help much appreciated

1987 RRC 3.5 V8 EFi

Cheers, Paul

Hi,

A couple of questions/thoughts - does it run for a couple of seconds then stall or just fire but never get going? (or something else all-together?) Does it pop and bang?

It should not be sparking exactly on TDC - it should be a few degrees before. Not sure on your engine but 7deg won't be far out...

Plug leads in the right positions is an obvious one to check - I STILL get this wrong after 40 years, but it usually produces pops and backfires.

Is the fuel pump running? When you turn the ignition on it should run the pump for a couple of seconds, then, when the EFI detects that the engine is sparking, it will switch the pump on again. If this isn't happening then it will stall after a couple of seconds running I think...

HTH

Roger

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The engine does fire up, revs to about 1000rpm then dies.

The firing order is definately correct, checked many times against Haynes manual. I rotated the dizzy to get it to fire slightly before and after and it didn't make a difference.

I took the spark plugs out and dried them with a cloth and gave them a quick brush, do they really need to go in the oven?

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Sounds like you may be missing the single wire from the AFM to the coil negative, this allows the cold start injector to fire, but none of the others, on a hotwire it is white/black, can't remember what it is on a Flapper, which I assume yours is, being a 3.5 EFI.

Other alternative it to manually hold open the flap in the AFM to make the ECU think it is running and then try to start it (need two people for this!)

Come to think of it, it's more likely the second option, as if the AFM doesn't show air going into the engine it will cut the fuel pump.

Hope that helps :)

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  • 2 weeks later...

Bloody relays!!!!!

After much cursing i finally got it going. It dawned on me that if it keeps starting briefly it is probably the cold start injector firing but not the others, so i checked them with a multi meter and lo and behold it was. After a bit of reading on diagnosis i saw a comment about not using Lucas type relays in place of Bosch type for the main relays, so when i checked i was using Lucas type so swapped it over and it fired straight away. The annoying thing is the Lucas type does click on and off when you turn the key which is why i thought it was fine as i previously had checked the relays, I must have swapped the correct Bosch one out at some point to make sure it wasn't faulty.

The timing was alright in the end, although i did get it wrong first time by not getting it on compresision stroke, what i did to check it was on compression stroke initially was just to take out No1 spark plug and feel for air being forced out, but now i realise this is stupid as even if the valves were open (which they were) air will still come out of the spark plug hole as the gap around the valves are much smaller, so from now on always remove the rocker cover to check!

Thanks for all the help

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air will still come out of the spark plug hole as the gap around the valves are much smaller

Remove No 1 plug and put your thumb over the hole while turning the engine front pulley - you can definitely feel the pressure as it rises on compression then :)

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