4D56 Help

[ee904age]

I've just scored a tidy L300 van for a good deal, however it has no compression.

It's got a 4D56 non-turbo, I knew it wasn't running when I got it and had the intention of pulling the motor from my rusty ute and chucking it in there.

Apparently the previous owner had run petrol through it, doing god-knows what damage, took it to a workshop who did a compression test, less than 200 psi all round, I'm thinking it should be close to 500 psi.

The old owner got a backyard mechanic to pull the head, had it welded where it had apparently cracked and then skimmed and put it all back together. He says they poured oil in the bores and it didn't leak past rings so assumed bottom end was all sweet. But, still no compression so I picked it up cheap.

Before I go ripping the old motor out, is there anything other than timing I should check? I've checked and double checked all Cam, Inj pump, crank, and balance shaft timing marks and everything is spot-on.

All rocker gear is working as it should as far as I can see under the cover.

Any suggestions welcome.

Cheers,
Shay.

[Lloyd]

"No compression" meaning around the 200 mark still?

[ee904age]

There was an invoice from a workshop in the van that said it had been tested, and all cylinders under 200 psi, how much under I'm not sure. The thing is, the head has been pulled since, and supposedly checked and fixed, and the rings/pistons/bores should be usable if the held oil no?

I cant think where it could be losing that much compression. It winds over like a petrol with no plugs in it, and I can turn crank with a 19mm spanner with not much effort.

If it had bent valves would it be visible under rocker cover? ie: a valve spring would stay depressed?

[Lloyd]

It doesn't take much for a valve not to seal, to the point that you can't always see it. Check clearances will give you a decent idea. Oil down the bores should be enough to seal the rings a bit, even if they were worn.

Leakdown test would be the best option really. Put engine on TDC, stuff air in which ever cylinder is on top of compression stroke and see where the air comes out.

[ee904age]

So, I made an adapter today to feed air into the glow plug holes and set regulator to 50 psi.

Number 1 cylinder, spewed air out inlet. Checked inlet valve, rocker not sitting in centre of valve stem, bad sign. Backed adjuster right off and tried again, engine turns over 1/4 turn. Likely bent valves, so backed off adjusters on all others.

Number 2 & 3 Cylinders just bubbled out around injectors, and couldn't get my adapter into number 4 as I made it too long.

So far it seems like to bottom end is okay, but valves are likely toast, which seems strange as after a bit of reading, these motors tend to break rockers when contact occurs.

Question is, would throwing a new set of valves at it do the trick, or do the guides normally get damaged aswell?

[Lloyd]

Something sounds a bit suspicious. If the head has been off then it should have been surfaced and pressure tested which would have shown any of these issues up.

[Crucible]

Are you sure your checking on compession stroke? As you will get air leaking into intake if just past tdc exhaust stroke as it will be starting to open inlet valve

Shouldnt matter if youre backing valves right off but will pay to check. Try and get opposite cylinders rocking so you know its def on compression.

1-4 and 2-3 and visa versa.

[ee904age]

That's what I thought. They said the head had been surfaced, which I assume is done on a bare head, not complete with valves etc?

If so, the damage must have been done after the head was put back on, which is a possibility, as the guys "mechanic" didn't seem like the sharpest tool in the shed, and may have cocked up valve timing, tried to start it, realized his mistake and put it right but it's too late, and just told the owner it has no compression, time to move it on.

[ee904age]

Are you sure your checking on compession stroke? As you will get air leaking into intake if just past tdc exhaust stroke as it will be starting to open inlet valve

Shouldnt matter if youre backing valves right off but will pay to check. Try and get opposite cylinders rocking so you know its def on compression.

1-4 and 2-3 and visa versa.

I can't get to #4 at the moment, but will shorten adaptor tomorrow and try it. #2 & 3 don't seem to leak other that out injectors now that adjusters are backed off.

[Crucible]

Generally you will have excessive valve clearances if the valves are bent as they jam in the guide. With the rockers being off centre it does sound like the case. Normally you wont have any compression what so ever though..

[ee904age]

Another possibility that came to mind is when it ran on petrol, it has over-
revved and stretched valve stems? Have seen it happen on bikes but not on a car engine.

Guess either way I'll need to pull the head and find out.

[rollaholic]

interesting its apparently got low compression on all cylinders but is only seriously leaking on one.

i would pretty much ignore / forget everything you have been told by PO and start from the start.

which it basically sounds like you are doing anyway.

[ee904age]

So, back to basics and taking on Lloyds advice about valve clearances, I reset them all within spec, pulled cam belt and started from scratch. Still haven't had a chance to find a socket to torque down injectors but now it has compression, enough to stall the starter on a half flat battery!

Will charge battery tonight, reassemble tomorrow and hopefully be back to its rattly underpowered glory!

[ee904age]

Update:

Found heaps of compression hiding between the valve stems and rockers, but still no go. I have pulled head and everything looks acceptable, although the bores have a slightly rusty colour to them, but no rust visible or anything I can feel with a fingernail?

The head gasket mating surface looks like it could have some remains of a previous gasket stuck on it, kind of a rough, sandpaper feel in a couple of places (current gasket is new, never been run).

I've put about 5mm of ATF on top of the pistons and cranked it back and forth a few times, will leave it overnight and see what's there in the morning.

If ATF is still there in the morning, I assume rings and bores should be good enough for it to run?

Any suggestions on how to clean gasket surface before re-assembling keeping in mind block is still in van and I don't want to strip or remove it?

I don't really want to spend any money on it other than a new head gasket (current one stuck to head in a couple of places) to get it running since I already have a runner in my daily ute. If it needs more than a gasket, I will swap engines and part it out.

[Lloyd]

If you have compression now then there is very little that should stop it going short of not getting any fuel. Easiest way to clean head/block is sandpaper on a block, or if it had been off recently and the bits come off nicely then use a blade to scrape everything off.

If you get it back together and it has compression then crack the injectors and crank it over to see if it's getting any fuel. If it has those then it should go.