86 defender 90 loss of power

hi all, just joined and have a niggly problem with my def 90 2.5 N/A diesel.
i rebuilt the engine earlier this year after one of the piston skirts parted company with the crown. 4 new pistons, new head, valves and rockers sorted it out.
anyway, it doesn't burn oil (bit of white smoke on startup) but it does seem low on power (i know its n/a, but it did seem to have more poke before the rebuild).
any ideas anyone? it's doing my head in now

How do Quattro. Do a search on here an somewhere theres a fred that tells you how to set the Injection Pump up to get better performance. I'm sure it was posted by Charlsey which may help in finding it.

hi quattro

I'd be interested to hear why you rebuilt the engine; did you consider replacing it with a 200tdi block? The reason I'm interested is that I have a 1986 N/A - running on 3 cylinders. It's decision-time for me: do I scrap her, repair her or re-engine her.....

Hello Quattro, (and Buck!)

I have a 1986 2.5 N/A 90 which was up until recently down on compression in one of the cylinders. My local specialist re-bored the cyclinder and installed a new piston under warranty which has helped its performance on the flat and up hills quite noticeably. Sinse the new piston, I have had an issue with loss of power (not related to cylinder) which was down to leaking fuel line plumbing. The banjo nut that screws into the top of the fuel filter housing had corroded and one of the pushfit inserts which the pipes are connected to had come loose without me realising. It had been sucking air into the system and thus starving the engine of fuel at high revs. It was only when I looked at changing the fuel filter that I noticed this problem. A new banjo nut sorted it out and now its running flawlessly.

Britpart supply new banjo nuts, but you can't just buy the nut on its own. It comes with the two fuel pipes attached which is a bugger cos it came to about 8 quid for some bits that I didn't really need.

Your best bet is to check the plumbing. A good way to see if there's any air in the system is to slightly loosen the bleed bolt / nipple on your injection pump (if it's a Lucas / CAV). manually pump diesel through the fuel line with the lift pump and see if any bubbles come out from around the bleed nut. If it's just fuel you're fine, and I've wasted 5 minutes writing this response!

Good luck
-Pos

CharlesY is yer man... find his posts about setting fine tuning the IP timing. Gold dust!

thanks for the reply's all, will do some searching on that pump timing trick.
we rebuilt the engine due to time being a factor, as it was required for use as a daily driver, and sourcing a 200tdi was not really an option due to this. if we had a couple of weeks in which to do the job then we would have sourced one and done it that way.
TBH i did think along the lines of fuel starvation, we did change the lift pump after the rebuild, along with the fuel rail (across the injectors) and the pipe back to the filter housing, although i suspect that it could still have an air leak somewhere - at least i have a few pointers now.
It was quite an easy job to rebuild the beast - although quite pricey as we had to replace the head due to it being severely pitted.

Adz said:

CharlesY is yer man... find his posts about setting fine tuning the IP timing. Gold dust!

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Hi ADZ,

Did you have a go at your timing set-up ?
If so, tell us what happened.
In some Landies it really makes them go if you get it spot-on.

His white smoke on start-up should be looked into, because the moment there's white exhaust smoke you know FOR SURE there isn't quite enough "heat of compression" to light her up, and on a cold morning he could end up battening his flattery before it starts. He needs BEST QUALITY glow-plugs (four of, copper-greased), give a plenty good long glow, and to remember to keep his foot OFF THE THROTTLE while cranking on the starter.

The glow plugs in a N/A do several good things, like heats up the pre-chambers, vaporises the fuel spray which raises compession pressure, and if still red bloody hot will light the fuel and make her run. Go direct from GLOW to GO on the key!

The moment the engine fires up, the pistons rise on compression so quickly that no heat is lost to the cold block and head, and compression ignition takes place. It's just at slow cranking speeds that things can go wrong if the heat build-up in the compressed air isn't quite hot enough to light the diesel. It vapourises into smelly white fumes, which can explode in the exhaust system by the way ....

A N/A 2.5 diesel set up to max is perfectly fine - no drag racer perhaps, but a tough working reliable engine that starts well, pulls well, and can keep up with the traffic.

CharlesY

Nope - no need on mine. It's a Tdi and pulls like a train (French train ofc, not the rubbish we've got over here). I've tweaked the fueling a little - will be increasing the boost when I can remember to be bothered to get under the bonnet for 10 minutes... 2bar boost guage reads a consistent 0.75 bar at max boost, so plenty there to play with.

Adz said:

Nope - no need on mine. It's a Tdi and pulls like a train (French train ofc, not the rubbish we've got over here). I've tweaked the fueling a little - will be increasing the boost when I can remember to be bothered to get under the bonnet for 10 minutes... 2bar boost guage reads a consistent 0.75 bar at max boost, so plenty there to play with.

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Turning the boost limit rod shorter may get you up to just over 1 BAR boost, but the injection pump max fuel limit setting will stop it getting any more. 0.75 BAR is not enough for best efficiency, and your ideal situation (which is hard to achieve) is a lot of boost when cruising along.

There's a fine balance to be made after that in turning up the boost AND hoicking in more diesel to burn so it makes more and hotter faster exhaust so the turbo runs faster and makes more boost .... and so on.

If you make a pig's arse of this it can go wrong, and one day towing a big trailer up a long hill you may find the crankshaft hits the tarmac.

I suggest you don't top 1.2 BAR , and it may not be able to anyway

CharlesY

I was aiming for a max of 1 bar... it's quick enough and torqey enough as it is at the moment to be honest. I'm not really after outright pace... if I wanted a road rocket I'd have bought another MR2 turbo, the last one was signficantly quicker than our new mates Supra turbo - and it went round corners

Since I fitted the boost gauge, I've noticed it makes considerably more boost while cruising than any of the turbo (petrol) cars I've owned in the past - typically around 0.5bar at a constant @60mph. The only reasons I'm going to increase it are a little more motorway overtaking 'punch' and because I want to find out what happens

It's still got a very clean exhaust - a tiny puff of black smoke on startup is all, none whatsoever either off boost or on it that I can tell from the drivers seat and I've had someone follow me watching for smoke from the exit on acceleration, there's none apparently, so maybe some more scope for a further increase at some point in the future.

Cheers,

Adz said:

I was aiming for a max of 1 bar... it's quick enough and torqey enough as it is at the moment to be honest. I'm not really after outright pace... if I wanted a road rocket I'd have bought another MR2 turbo, the last one was signficantly quicker than our new mates Supra turbo - and it went round corners

Since I fitted the boost gauge, I've noticed it makes considerably more boost while cruising than any of the turbo (petrol) cars I've owned in the past - typically around 0.5bar at a constant @60mph. The only reasons I'm going to increase it are a little more motorway overtaking 'punch' and because I want to find out what happens

It's still got a very clean exhaust - a tiny puff of black smoke on startup is all, none whatsoever either off boost or on it that I can tell from the drivers seat and I've had someone follow me watching for smoke from the exit on acceleration, there's none apparently, so maybe some more scope for a further increase at some point in the future.

Cheers,

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Sounds great.

With a diesel engine, the more air you can ram in at any stage of the game, the better it will run, and the more efficient it will be. The higher the effective compression ratio, the better. A diesel doesn't need to worry about a fuel-air mix ratio, so a diesel can run at full boost even when cruising along at light throttle.

Using a turbo diesel, having a very high top gear allows the engine to run at slow revs with a good dose of throttle, and that can enable high boost pressures at cruising speeds, which is good. A bit of throttle at low revs and high boost may end up more economic than less throttle at higher revs with lower boost. If you get the idea!

Sounds like you've got your one more or less maximised. I bet one tiny dab of the GO pedal whips the turbo pressure up right smartly.

Charles.

CharlesY said:

Sounds like you've got your one more or less maximised. I bet one tiny dab of the GO pedal whips the turbo pressure up right smartly.

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Once it's moving it's never really off boost and yes, press on the loud pedal and i'll hit max boost on the gauge almost before you feel the car start to accelerate. I still need to plumb the waste gate and gauge into the induction manifold side of the intercooler so I'm getting a proper 1 bar into the engine rather than just at the turbo - an EGT probe and temp gauge would be a nice idea to help set it up properly, but I've no idea where I'd be able to get one.

The only point where I get a bit of lag is pulling away from a standstill... but with 1st being so low geared it's hardly a problem, once it's rolling in gear it's making boost more or less all the time.

Cheers,