daz tree cutter Posted July 24, 2017 Share Posted July 24, 2017 Hello I am new to this forum I have recently purchased a 1970 mk 2 defender with a 3.9 v8 range rover engine in. The engine is from a 1992 rover. When accelerating it will only get to around half revs and then it is like the engine is restricted! I have cleaned the spring on the rear of the air intake and replaced the fuel filter. Starts first time and runs up lovely just wont rev over half. Sorry haven't got a rev counter in. Can any one offer some advice please Cheers Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted July 24, 2017 Share Posted July 24, 2017 Fuelling or ignition. My money is on ignition, if only because that's usually the problem with old RV8s. Do you know what type of ignition is fitted? It's probably going to be using a distributor, but there are different variations, and it might not be what came out of the donor Range(?) Rover. If you're not sure, get us some photos so we know what we're talking about. It could simply be that the timing isn't set right, or the vacuum advance in the distributor has failed. Other possibilities would be inadequate fuel pressure, I guess a worn camshaft, or a restriction in the air intake, or failed sensors if it's running the original hotwire engine management system (or any other for that matter), or if it's running an aftermarket ECU the mapping may not be set up properly - but let's check the basics first. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 25, 2017 Share Posted July 25, 2017 Young Steve is currently experiencing a very similar problem: I'm with Geoff on both vehicles! Quote Link to comment Share on other sites More sharing options...
daz tree cutter Posted July 25, 2017 Author Share Posted July 25, 2017 Hello and many thanks for the advice. I will have a look tomorrow and let you know about the ignition system. Cheers Quote Link to comment Share on other sites More sharing options...
steve200TDi Posted July 26, 2017 Share Posted July 26, 2017 I was thinking the same thing! It does sound similar! Steve Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted July 26, 2017 Share Posted July 26, 2017 My first check given this scenario would be to check that the vacuum advance is working.... a small pipe going from the dizzy to inlet plenum... remove it from the inlet plenum and suck on it.... it should feel restricted... if you can suck n suck on it the rubber diaphragm is split hence not advancing the ignition..... Quote Link to comment Share on other sites More sharing options...
paintman Posted July 26, 2017 Share Posted July 26, 2017 (edited) As it's a converted vehicle & we don't know what else might have been done there's a few things that need to be established. Is it carburettors or fuel injection? Does pressing the accelerator to the floor fully open the butterflies - one in each carb if on carbs and just one in the mouth of the plenum if EFi? Carburettors may have a restrictive device fitted. If it isn't on carbs you can ignore this one. Is it manual transmission or has the conversion included automatic gearbox? What - if anything - did the previous owner tell you? Was it like this when you test drove it? Edited July 26, 2017 by paintman Quote Link to comment Share on other sites More sharing options...
steve200TDi Posted August 1, 2017 Share Posted August 1, 2017 I've just fixed my V8, it was the ignition amp - it may have failed or it was a poor earth. Steve Quote Link to comment Share on other sites More sharing options...
neil110 Posted August 1, 2017 Share Posted August 1, 2017 If your amp has failed I would consider changing the coil as well. I went through 3 amps in fairly quick succession until I realised it was the coil that was killing them Quote Link to comment Share on other sites More sharing options...
steve200TDi Posted September 7, 2017 Share Posted September 7, 2017 On 7/25/2017 at 8:47 PM, daz tree cutter said: Hello and many thanks for the advice. I will have a look tomorrow and let you know about the ignition system. Cheers Did you sort it?! Always handy to know the outcome/fix! Steve Quote Link to comment Share on other sites More sharing options...
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