Finished the 300TDI swap - some problems/questions - Defender Source
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Old October 11th, 2010, 11:34 AM
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Jason Herring
94 D90 ST #1253
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Finished the 300TDI swap - some problems/questions

So my 6-month (from rip to replace) effort to swap a 300TDI into my truck is done. Now, since I've never owned a diesel much less driven a 300TDI I have some questions/issues as I try to get it running 'right' (since I am not sure what 'right' feels like for this setup).

300TDI, 75K original miles, rebuilt head (but otherwise original), R380 trans in my '94

1) inconsistent startup

When I first installed the engine it required more cranking than I thought right to get it to fire up. I then hooked up glow plugs but it still started sluggishly. Later, after driving for ~30-40 miles it started firing up with barely a touch to the key. Great! But now, at about 200 miles, it's back to crank-crank-crank and slow startup again.

The tank was completely empty of old fuel, as were the lines. The lift pump is original. The filter that came with it looked clean when looking down into it but I can't tell if it's new or used. The injectors I believe were not serviced. Thoughts?

2) vibration

The motor seems to have a high-frequency vibration (buzz) which transfers to the chassis I wasn't used to with the V8. This might just be a TDI thing?

3) acceleration

The acceleration is not great at low RPM as many here mention. However, when at middle-speeds and between 2K and 3K RPM I get very little 'umph' where I expect the turbo to pull best - it feels very 'flat'. I added a boost gauge temporarily to see if I had a problem there and it's pushing up to almost 15PSI, which seems normal. Just no real 'pull'. I moved the waste gate signal pressure line from the turbo housing to the intake, which made a small but noticeable improvement, but the general flat spot still exists.

I don't have EGT or oil temp gauges, but I suspect it's getting hot from monitoring the oil pressure (engine water temp is fine). At startup I get 45PSI, once driving and 'warm' I get 35PSI when accelerating around side streets (down to a minimum of 20-22 at idle when warm), but on the freeway when holding 65 (which it does with some difficulty) the oil pressure at load RPMs goes down to about 20PSI. Once off the freeway and back to side streets for a bit (and thus cooling down) the oil pressure goes back up to 30-35PSI.

I'm worried it's running lean and I don't want to damage the engine.

4) new problem today - rough idle

I adjusted the fueling per the TDI tuning guide 'stage 1' (see my other post) by rotating the torx stop screw on the boost compensator 1-1/2 CW turns from factory. This made a small but noticeable improvement in off-idle acceleration (I haven't adjusted the star-gear yet for 'stage 2' tuning). However, I now have an issue idling - the engine sometimes drops down to 500rpm and shakes quite a bit at idle as if it might die.... then goes back up to 750rpm and idles smoother. This could be coincidental with my adjustment, or maybe not.

5) oil leak at EGR block-off

When I first fired up the engine I had oil trickling down from the EGR block-off plate. I replaced the gasket and this went away - but should there really be oil there in the first place? Also, I noticed that there was some oil (not soaking wet, but moist enough..) in the intake when I relocated the wastegate signal to the intake from the turbo housing - I'm hoping this doesn't mean a blown turbo oil seal. The intercooler was used and could have had some residue/old oil in it I suppose but after this much driving I'd think that would be gone by now. I don't have any excessive black smoke (occasionally a very small puff when shifting gears probably, I had my g/f follow me for a few miles), even after my adjustment of the fueling.

Oil consumption when I first started the engine seemed like I lost a quart pretty quickly (but then I couldn't remember if I checked immediately after topping off & got the oil circulated fully though the oil cooler, etc), but then went for some time with no oil loss. Then later I checked again and it was down a quart. I did locate a leak near the oil pressure sending unit I added (installed a "T" for idiot light + gauge) and corrected that & haven't had enough time since then to see if that was the cause of the oil loss.

5) Los Angeles area 300TDI check up/tune-up

Is there a shop in LA which I could take this to in order to get it dialed-in properly (or at least properly diagnosed)? Maybe I'm going in circles and should let someone who knows these engines really well get it tuned properly for me.

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Old October 11th, 2010, 11:40 AM
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First thought on your starting is an air leak in the fuel system. Worth looking into.

Oil pressure sounds normal.

Tdi's use a little oil normally. but it should not be excessive. Is the smoke blue? If your not burning it it is leaking.

welcome to slow noisy and efficient

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Old October 11th, 2010, 12:59 PM
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Doug Crowther
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It sounds like you have basic but easy start up gremlins.

1) crack the bleed screw on top of the fuel filter housing while the engine is idling. If fuel doesn't come out and the engine falters or stalls your lift pump is shot and the injection pump is both pulling fuel from the tank and pressurizing it for the injectors
2) If fuel does come out have you changed your fuel filter yet after the initial couple hundred miles ? Hard starting on engines that run well once started is usually filter or air leak related like Steve indicated.
3) if fuel to the injection pump isn't the problem then injection timing may be- did you change the belt or check it ?
4)I think you will find turning the diaphragm in the ip will make a signifigant difference. The engines tone even @ idle usually sounds smoother and less labored.
5) the sound you describe could be a tensioner pully bearing,water pump bearing, or even an alternator bearing. I had the same problem and with a mechanics stethescope was able to track it down to the alternator which was working fine. i replaced it witha disco 100 amp unit and the noise went away.

hope thats helpfull. Oil pressure sounds spot on.
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Old October 11th, 2010, 02:08 PM
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Originally Posted by 130Tdi View Post
Oil pressure sounds spot on.
Doug........should the oil pressure being going UP or DOWN with acceleration and higher RPM's?? I thought UP as the pump is working gauge pegs up with any increase in RPM's.

Regardless, I wouldn't think any of these problems are related to oil pressure.

Jason, as I'm sure you know, an EGT gauge is one of the most important gauges you should have especially if you are making adjustments to your engine. It's incredible how you can't feel or hear the engine working but how quickly the temps spike with changes in engine load.

I would bet your timing is off and would definitely check the belt with 75K on the engine.
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Old October 13th, 2010, 11:30 AM
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Jason Herring
94 D90 ST #1253
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Slow, noisy and efficient, here I come!

Thanks for the info - the explanation regarding the IP makes sense. Yes, it was running fine at higher RPMs but idle and startup was bad.

OK, so it looks like I have been getting some air in the system somehow - when loosening the bleeder on the fuel filter almost nothing came out (a burbling) for a good 30 seconds... then it started spraying all over like crazy. Apparently I have succeeded in bleeding out the air at this point because now it starts/idles good (at least, immediately after I did this... haven't driven it anywhere yet since).

How does the air get in? Is this a case of a weak or defective lift pump? I bled the system when I first fired it up with the manual priming arm on the lift pump. I don't know where else air could be getting in that I'd not see a leak in the diesel fuel lines. Maybe I should replace the pump for good measure... I should probably do this as a starting point (along with filter) before messing with the fueling further?

I plan to get an EGT eventually - I just don't have anywhere to mount it now = another project (new center dash probably). I won't do any more 'advanced tuning' on the engine fueling without one after your advice.

Oil pressure goes up with RPM but down with rising oil temperature - which is why I was concerned that it was getting hot when under load on the freeway because the high-RPM pressure was not much higher than the low-RPM pressure (though the mimimum never goes below 20.. it seems to me that under high RPM it should be higher than that even if hot-ish). Higher RPM should somewhat offset the pressure loss by oil temperature... so my thought was fueling was lean, making it hot under load and boost..?

In the past I've had a chronic problem with the old 3.9L overheating so I'm paranoid about temps it now. Maybe a second stage oil cooler like those they install with aftermarket full-width radiators/intercoolers....
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Old October 14th, 2010, 07:57 AM
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Jamie Austin
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Try (whilst the engine is running) loosening the bleed screw on the top of the filter housing. crack it open and fuel should seep out.

If nothing, remove it some more (until it comes out totally) if no fuel comes out (and you peer into the hole and can see the filter 1/2 full or so) then your lift pump is on its way out. easy and cheap fix, and makes a world of difference to your engines running.

my point is, looking into the filter and seeing it half full would make you think that there is an air leak, when it could be the lift pump.

Although from what you're saying, when you cracked it open you got a lot of fuel spurting out eventually, which would lead me to think that the lift pump is OK. maybe there's a split or hole in the plastic fuel pipes, or the pick up in the tank isn't long enough and is sucking up air???
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Old October 19th, 2010, 12:12 PM
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Jason Herring
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I did that, and it nothing much came out at first (just the smallest amount)... then after a few moments of idling it came out more and more until it started spraying and I had to tighten it down to prevent getting fuel all over the place. The amount coming out definitely 'ramped up' with time. If all was good should it have been pushing a lot of fuel from the beginning?

I am waiting for the parts to arrive (this stuff is pretty much mail-order... unless there is a parts cross-reference to something more common...) but in the mean time I'd like to know if there is some other air leak. I don't see evidence of fuel leaking anywhere, which I'd think I'd see if it was leaking.

After the apparent fuel system bleeding I did when testing this the truck ran good, idled good and started right up. Now I've been out of town for a week, I came back and started it up but I'm back to a very poor idle again. I'm thinking that air may have leaked back into the system? But there's no sign of spilt fluid.

My fuel system was pieced together - adapted from 1/2 300TDI system and 1/2 NAS as this was a conversion. I put a new fitting in the top of the tank insert (the old feed line fitting was rusted so badly it broke when loosening the old fittings). The pickup is long enough - I used the original orange plastic flexy-hose that goes to the fuel pump spliced to a piece of the black plastic fuel line taking the place of the fuel pump (with a pretty tight hose clamp) so that when the fuel tank insert goes in (it's spring-loaded - PITA!) it gets pushed snugly to the bottom. I messed with this for an entire afternoon and think it's on there pretty good.

The NAS fuel filter has been replaced by a piece of straight plastic piping, though I'm thinking of putting a sediment filter in that spot at some point.

No visual signs of fluid leaks anywhere but maybe I need to look closer...
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Old October 19th, 2010, 07:03 PM
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The stock 300 Tdi has a sediment filter on the right rear wheel well. Probably a good idea to install one at some point but also probably not one of your problems. If you have oil coming out of your blanking plate then you may have too much oil getting into your intercooler. If that is the case then your turbo could be weak or your breather clogged. Do you have black smoke at start up? Does it dissipate rather quickly? Under acceleration do you have a small tint of black smoke? If your does these things then it is quite normal. If it is really black for a long time then something is out. If the smoke is whitish blue to blue then you may have other problems. If you do not know the age of the timing belt...I would change it. Make sure that you get the new belt modification kit. It comes with all the pulleys and the belt.
My 300's are not the fastest in the world and have a sweet spot in the RPM band. It is only a 4 cylinder so the sweet spot might be a little higher than we think. Mine pull real fine at 2,000 RPM
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Old October 21st, 2010, 03:33 AM
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Jason Herring
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There is barely a puff at startup, and I had the g/f follow me around the block and she said "once in awhile" (probably shifting gears/accelerating etc) it makes a small puff of blackish smoke.

Nothing blue.

The breather - could be clogged, dunno, it's not new. I can take it off and clean it? Or is that a replacement item? There was a decent amount of oil dribbling down from the EGR block-off before I changed the gasket - enough that it caused some smoke in the engine compartment from hitting the hot exhaust. Yeah, I'm hoping the turbo bearing seal isn't shot...

Still waiting for my new lift pump and filter to arrive. I may install an aftermarket sediment filter - the OEM one is over $100, which seems crazy-ish.

Mine definitely has a flat spot in the power band at 2000rpm - once I solve the idle problem I'll check fueling/timing.
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Old February 21st, 2011, 09:14 PM
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What was the outcome of this? I'm interested in a tdi swap and i think your issues would be good to know about.
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Old February 23rd, 2011, 01:37 PM
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Dave C
1983 110
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Putting a 15psi gauge under the hood in the lift-pump line makes for a very easy check of the fuel-delivery status. Given all the probs with Tdi lift pumps, I'd replace it as a matter of course, or just fit the mrgasket (diesel-specific) electric lift pump and never think about the pump potentially being the problem again.

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