task Posted April 26, 2009 Share Posted April 26, 2009 I have a 1991 3.9 V8 fitted into a Series 3, the engine currently has fitted a hotwire injection system. The engine is timed to TDC, new spark plugs and gives a good spark. It has the standard range rover in tank pump. The engine starts and runs up to temprature but present the two very strange problems. Firstly the engine has a flat spot at just above tickover, if you push the throttle it's like the management system takes a little time to respond and it will splutter, do this enough times in quick sucession and the engine will stop. Second issue, if the engine is turned off from the key it will start without issue. If the engine stalls or is otherwise stopped without using the key it will not start. There is a good spark during this period. The following has been replaced; ECU Engine coolant sensor Fuel thermistor AFM Throttle Pot The idle air valve has been removed, cleaned and refitted. If removed you can see it moving out and back in again. The battery presents around 14v when running. I'm currently preparing a pair of SU's and a manifold to fit as I've run out of ideas with the EFI. Any suggestions welcomed please! Quote Link to comment Share on other sites More sharing options...
Dave W Posted April 26, 2009 Share Posted April 26, 2009 Do you have a way of checking the fuel pressure ? Just wondering if it's running over pressure as that would leave it running rich and the problem would be increased by the extra fuel going in when it sees the throttle increase, causing it to stall and flooding it making it difficult to restart. The two main causes for over pressure are the regulator unit or restricted return pipe (the lining of the rubber pipe can collapse, restricting the return). The other thing that comes to mind is if one of the air pipes is split. Quote Link to comment Share on other sites More sharing options...
SteveRK Posted April 26, 2009 Share Posted April 26, 2009 Timing should be 4 degrees before TDC with Hotwire. It sounds like you have one of those annoying problems that could be due to any number of things - Ive been there and still am with my engine. If the vacuum advance isn't working this might cause a stutter if you are opening the throttle quickly - dabbing the pedal. If it stutters when very slowly opening the throttle then this has to be a mixture (fuel) related problem surely? Quote Link to comment Share on other sites More sharing options...
task Posted April 26, 2009 Author Share Posted April 26, 2009 It's when dabbing the pedal, in comparison to my 3.9 disco it's a world of difference. I should add I've replaced the dizzy too. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted April 26, 2009 Share Posted April 26, 2009 Shall I be the first? Ok then....You could convert to Megasquirt... Quote Link to comment Share on other sites More sharing options...
Dave W Posted April 26, 2009 Share Posted April 26, 2009 Shall I be the first? Ok then....You could convert to Megasquirt... I avoided suggesting that on the grounds that he's changed everything that MS would replace already so could end up putting MS on and having the same problem... albeit with better diagnostic facilities ! Quote Link to comment Share on other sites More sharing options...
LittleBlue88 Posted April 26, 2009 Share Posted April 26, 2009 Before i stripped the RR,i also noticed a studder when just slightly opening the throttle but just put it down to a hotwire system with 148k behind it.....worn As with regards to the lack of start after stalling,my boss's old 90 V8(3.9i) used to do the exact same thing,massive overfueling,found more fuel in the sump than in the fuel tank! Never got to the bottom of it tho,he just sold it Quote Link to comment Share on other sites More sharing options...
task Posted April 26, 2009 Author Share Posted April 26, 2009 Cheers for the replies, I'm going to throw on a pair of SU's for the moment I think, see if that solves the problem. If it does then I can MOT it and consider my options once I can drive it far enough to get out of second gear. I have considered MS and will likely give it a try once I've driven about a bit. If the SU's don't change anything then I guess I'll be taking the engine back out Quote Link to comment Share on other sites More sharing options...
LittleBlue88 Posted April 26, 2009 Share Posted April 26, 2009 I doubt its going to require engine removal,just a bit of thinking thats all Quote Link to comment Share on other sites More sharing options...
Dave W Posted April 26, 2009 Share Posted April 26, 2009 Cheers for the replies,I'm going to throw on a pair of SU's for the moment I think, see if that solves the problem. If it does then I can MOT it and consider my options once I can drive it far enough to get out of second gear. I have considered MS and will likely give it a try once I've driven about a bit. If the SU's don't change anything then I guess I'll be taking the engine back out If you're going to use the same fuel pipes (with a different pump obviously) make sure you check the return pipe is clear as hooking the SU return up to it will give you the same problem otherwise as SU float valves won't close if they have too much pressure and you'll end up with petrol pouring out of the overflows. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted April 27, 2009 Share Posted April 27, 2009 Look in the tech archive for the hotwire EFI diagnostics guide and work through every step, report back anything not right. Shouldn't be too strenuous, there's not a lot to the system. Quote Link to comment Share on other sites More sharing options...
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