paul mc Posted November 28, 2010 Share Posted November 28, 2010 Hi, I had a problem with no oil pressure which i have now sorted but now my engine isn't running well at all, it's a 1987 3.5 Efi flapper. It is running well, although a bit fast at idle, on LPG but very very badly on petrol, also i have had to set the timing very advanced for it to run at all whereas it used to run pretty near TDC. I am guessing the bad running has something to do with timing as i did have the dizzy out while priming the oil pump but i think i have put it back correctly, if i use the timing light i can get cylinder 1 to spark bang on TDC by turning the dizzy but the engine will not run, as i said it needs to be very advanced to run. I will change the fuel filter tomorrow as a matter of course, it needs doing anyway, but any one got any other ideas what could be causing the problem? I Have disconnected the fuel lines and petrol is getting to the engine, although i can not confirm at what pressure. Any help much appreciated. Quote Link to comment Share on other sites More sharing options...
Quagmire Posted December 16, 2010 Share Posted December 16, 2010 Sounds obvious, and I apologise if you have checked this already, but have you got all the leads on in the right place, right direction of rotation etc? *edit for clarity. What I meant to say was that just because pot1 is correct, are the others? Quote Link to comment Share on other sites More sharing options...
Quagmire Posted December 16, 2010 Share Posted December 16, 2010 Oh, and what did you have to do to sort the oil pressure? How much of the engine had to come off? That'll help pinpoint what other parts could be involved... Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted December 16, 2010 Share Posted December 16, 2010 I think you have probably got the dizzy one tooth out,best to use the w/shop manual to start from scratch - #1 at tdc on compression,fit dizzy as per instructions then check the ht lead order. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted December 16, 2010 Share Posted December 16, 2010 But it runs fine on LPG? I'm assuming a draw through system, which points to a fuelling issue on the Flapper, which will start with saying coolant temp sender Quote Link to comment Share on other sites More sharing options...
paul mc Posted December 16, 2010 Author Share Posted December 16, 2010 Oh, and what did you have to do to sort the oil pressure? How much of the engine had to come off? That'll help pinpoint what other parts could be involved... To sort the oil pressure i only took the dizzy out so i must have put it back incorrectly. I do think it's timing too, i will start the timing from scratch this weekend and hopefully sort it out. I did check the order of the leads and they are ok, i also got a new dizzy and rotor arm as the old ones were OK but a bit worn down. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted December 16, 2010 Share Posted December 16, 2010 In removing/refitting/rotating the dizzy, have you managed to get it so the rotor arm is pointing one cylinder ahead/behind where it's supposed to be - you can have a spark happening at TDC but the rotor arm pointing to the wrong HT lead. Is the timing otherwise OK - advancing properly and whatnot? Quote Link to comment Share on other sites More sharing options...
Ragtag Posted December 18, 2010 Share Posted December 18, 2010 It is running well, although a bit fast at idle, on LPG but very very badly on petrol, also i have had to set the timing very advanced for it to run at all whereas it used to run pretty near TDC. I am guessing the bad running has something to do with timing as i did have the dizzy out while priming the oil pump but i think i have put it back correctly, if i use the timing light i can get cylinder 1 to spark bang on TDC by turning the dizzy but the engine will not run, as i said it needs to be very advanced to run. My 3.5 is on carbs so it may be different for an efi engine but static timing is 6 degrees BTDC for petrol anyway not TDC. LPG tollerates (indeed thrives on)as much advance as it can get, I run about 20 BTDC but at that level it is a dog on petrol. How advanced is your 'very advanced'? I wonder if you have actually got it running more advance than you think due to an incorrect starting position with the dizzy. Either that or Bowie69 is right and a random efi problem has forced itself into the equation just to confuse things. Quote Link to comment Share on other sites More sharing options...
pw8757 Posted December 21, 2010 Share Posted December 21, 2010 LPG burns more slowly than petrol, so requires the spark to occur earlier in the ignition cycle to ensure that the full power of the explosion is at TDC. Most conversions are set up to get the best (or worst) of both worlds, depending on your point of view. By setting "very advanced" in your description, you are probably getting the best from LPG. However, even on petrol, the spark should always take place some degrees before TDC so the petrol has time to ignite. If the spark is occurring at TDC on LPG, it is too late to give sufficient power. Other checks - is the vacuum advance working? You can check this by sucking on the tube that goes from the distributor to the air inlet pipe. You should see the spring move. HTH Quote Link to comment Share on other sites More sharing options...
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