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Mega Fireup but poorly V8 engine


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Well finally this morning after 10 months finally fired up the megasquirted v8 in the 90. Must be one of Nige's slower customers

I did fall into the trap of putting the coil feed on a terminal thats not live on cranking, then subsequently on a terminal thats only live when cranking!!!! Got there in the end though.

Somewhat disappointed though as the engine ran badly, popping and banging its way along. Gradually improved with temperature but still not right missing and generally beggaring about.

Must confess it wasn't good previously on carbs, and the ignition system was mackled by the previous owner so didn't have alot of faith in it.

Anyway I don't have a lambda sensor fitted at the moment so thats the next job to see if thats gives an indication but have a horrible feeling there is something more amiss.

Local garage compression tested if for me and said it was ok but been told thats normal with rv8's and everything else is kerry packered. So knackered heads or cam? Burns oil so could be leaking oil into the bores from the valve stems, there was carbon in the rocker covers, wouldn't have thought thats enough oil to make it run badly

So buy another engine to fit whilst I rebuild the currrent one, or buy an engine and rebuild it prior to fitting, or just recon the heads and fit a new cam, lifters etc.....

Any advice or opinions?

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Have you definitely got the leads on the right plugs/coils?

If the engine ran like a dog on carbs, Megasquirt won't cure a tired engine. If the vehicle is a keeper I would go the full rebuild if your current engine is a series of question marks in the reliability and wear stakes

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Whilst running

Squirt WD40 direct on exhaust manifiolds, if it burns off INSTANTLY then cylinder is firing, if it statys damp then there is either no fuel / spark ie missing on that cylinder

Do on them all, note which are OK and which not and post up

DO NOT start tearing engine apart yet !!!


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Do the exhaust header test nige suggested- you might have a stuck injector. With the engine running feel the injectors one at a time, if they are opening you will feel a definite clicking.

7 of mine were stuck closed when I first tried to fire up!

A sharp tap to the injector body with a soft drift and a hammer soon freed them off.

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Perhaps the edis is ok as I assume those cylinders are all on different coils so the other cylinders are working.

If can get an assistant will check the spark at each plug and do a continuity test on the injector wiring. Also found out I had been a numpty and mixed my left and right and wired the injectors into the wrong banks on the relay board

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Right have managed to grab a few minutes in the garage before dashing off to another family do. Just been checking the voltage at the injectors and relay board. There appears to be 12v at the plug with it disconnected on both wires and seems to be the same for all (can't easily get at some) is this correct or does that point to some of the injectors being stuck.

Thanks for advice so far its been a big help

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Right, loafs of wiring checking and out with the multimeter.

Looks like nothing happening on cylinders 1 & 6. Thought it might be the coil pack as these look like they are on the same coil. So swapped the packs round but problem persisted. Checked the voltage to the packs and the continuity of the wires to the edits and all seems ok. So am starting to wonder if its the edis. The injectors all appear to have voltage so might be a call to Nige later in the week

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Right well after talking to Note I am waiting for some plugs and a noid tester to turn up. Shame they didn't make it for the weekend. So decided to post some pics.

Pic of the truck with its new Purely Metal hoops to replace the old hardtop

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Started installing the ms kit nearly 10 months ago but the arrival of a new baby slowed progress. Then getting some brackets made up even slower. Wish I still had a mig.

Anyway truck has a half chassis td5 bulkhead and dash. Fitted with a 3.9 v8 originally on su`s (yuck) and a Borg transfer and auto. I bought it with all this and original hardtop nearly 18 months. Its always run badly, so being an engineer wanted to do something better but was sceptical about wiring.

So after lots of reading decided ms was the right solution

There were still some other jobs to do. The wiring was a mess, combo of td5 and old 90 mashed for the v8.

The lift needs to come off so it will fit in the garage, and the exhaust, though with tubular headers is a mess. Might replace it with a griffin system if I get some cash or try and come up with a better system using std Landrover parts and manifolds (any suggestions)


A new old stock has filter box. Tried to buy the proper bracket but expensive and n/a so had to design some.


A mechanical engineers nightmare. Anyway have a nas console to hide it all


Install awaiting finishing. Need to sort out the misfire first. Apologies for the photo,s from my new phone and the lights at the front of the garage have died. Another job

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A v8 question. Thinking of building a new engine but most engines appear to be the serp type. With my radiator and leccy fan setup everything a bit tight. Had to mod the water pump pulley with the vee belts.

So are serp engines slightly longer?

If so is there any reason why it can't be swapped to vee. Is there anything to watch out for?


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Right. Quick update as had a spare hour between jobs. Used the noid tester and checked the two non running cylinders plus the others I could easily get at.

All the injector signals appear to be working OK.

So changed the plugs to new bpr6es and fired up again.

Cylinders 1 & 6 still appear not to be working, cold headers with wd40. The header for no. 8 also seems cooler than the others too. So plugged one of the inline spark testers and that confirmed a spark on cylinder 6 and 8.

So it seems like its possibly stuck injectors. So plan I is to swap the three offenders for 3 of the known good ones and salvage a couple of others from another rail. At least if the ones from the new rail don't work I will know its probably the injector. Disappointing as I had all the injectors recon`d with new pintles etc before starting

If its not that then I am a bit stuck.

On the plus side the tacho I wired in appears to work off the edis (idm?) wire.

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Right well a busy morning swapped the injectors on 6 and 1 for ones from the cylinders that were getting hot, and substituted a couple of spares in the now empty slots

Unfortunately no better. Headers 1 and 6 still seem cold. Running below 1400 rpm is accompanied by popping and banging and above 3000 when cold.

Tweaking the idle screw in and out does not change idle speed much as well.

Coolant temp seemed to take a long time to change, but then it is blooming cold. Can you change it on megstune to read degrees c rather than f?

Am wondering now what is wrong as I mentioned it always ran badly before ms and put that down to rubbish ignition, crappy su`s and an efi fuel pump pumping so much fuel into the carbs it stank of fuel permanently.

Anyhow still seems to have problems.

Could it be mechanical? Knackered cam?

Attached a video for now


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Thanks Quagmire. Beginning to lose patience with this lump now. Had a chat with Nige today about this and some other things.

Am almost at the point of pulling this one out and finding another engine. At least I can rebuild this one at my leisure then, just really need to get the defender running again to preserve my sanity....

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