No warm start no joy-new engine

[stopping]

The engine starts fine cold in the morning. Dos not start at all after being run for 30sec - 30min.

 The timing is good.... cam very accurate, pump at .039" checked and double checked.... different pumps tried, different injectors (both: same results as the previous ones), the engine has been run from a jerry can so no restrictions, the solenoid plunger has been pulled, good glow plugs, seeming good cranking speed, the engine is really new... about one hour of idling total.  Deck height is .62mm (max) and using a one notch gasket. Cranking speed is good but engine is tight and the starter is working hard.

The engine sounds great and it seems to have power particularly in the low end. Smokes a bit when gunned (blue-white) I have driven it around the block a couple times... I have bled the coolant system according to the Vanagan voodoo standard. What else......?

I would like to know why it does not start warm. I should say the last engine did the same thing.... when driven hard it would be difficult to start imediatly afterwords but this is bad.... it will not start at all. The head and the coolant set-up or the same since rebuilding the bottom end.

I am trying to be patient any advice welcome.

Stv

[theman53]

Starter or grounds to the starter/engine. Start there. Or a weak or junk battery. I thought my flat red rabbit starter was fine, but after rebuilding it 2 times I got a reman from advanced the 3rd time...world of difference.

[stopping]

Thanks 53...

Can anyone explain why it would be more difficult to start warm than cold?

Stv

[rabbitman]

With my car cold starts are faster because the GPs get hot, when the engine is up to temp the GPs won't come on and since my timing is a bit retarded it cranks a bit. Pulling the cold start knob fixes that.

[Rabbit TD]

Thanks 53...

Can anyone explain why it would be more difficult to start warm than cold?

Stv

If it's getting fuel and it turns over ok I'm betting it might be valve related, maby the adjustment is on the tight side and when warm it keeps them off the seat enough to not seal.  This is a 1.9 though isn't it?  Didn't they all have hydraulic lifters though?  I don't know if a hydraulic lifter could cause that or not, it would turn over faster than normal though I'd think if not sealing right too.  Possibly the valve guide clearance a little tight not letting it close.  When you say the other engine did this too is it a completely different engine or does this engine have the other ones head on this engine?  If so the problem is probably in the valves not sealing for some reason.  Possibly a machine shop problem when grinding the valves sinking them deeper in the seats and not trimming the stem for the right clearance but at this point we have no idea what  or if anything was done to the engine or head.  If you are sure you have fuel and compression and timed close it should run and if not one of the 3 isn't there at the time.  Tell us more about the head and if it was rebuilt when building this engine.  How long does it have to sit before it will start again?

[stopping]

Oh yes it is a AAZ 1.9TD in a Vanagon. I guess I need to re-do my signature. The head I have had for three years now.... I took it to a machine shop where they "tested" it and resurfaced it slightly. I don't what testing it involves but I would think it valve clearance/ holding pressure is part of it. They said the head was good.

The engine is a whole other block that I had machined for new 79.98 Kolbenschmidt pistons, new bearings main and rods, new rod/pin bushings, seals, I had the crank machined for the TDI "D" gear.

It does have hydraulic lifters yes the head  is suspect because it is from the last engine..... I had to buy lifters for it when I bought the head... could they be the wrong size?

I have to leave the engine to cool for about an hour before it will start again.

[theman53]

Maybe the cylinder pressure is higher when warm? Or the weak battery/bad cables/starter doesn't like a quicker burn in the cylinder? Those are my guesses to why it would start harder warm.
Also, see if your glowplugs come on when it is warm. That would do the same thing as above B/C the fuel would light way before it was supposed to and act like an over advanced condition...but it should slow cranking a little too...
My money is on the Battery connection to starter or starter itself.

[Rabbit TD]

It sure sounds like valves not sealing to me from what you have said so far and about a half hour is about right for them to cool down enough to shrink a few thousandths to get back to seating.  Pressure testing is a method the machine shop uses to test the coolant passages in the head to see if it will let compression escape into them, that's what happens when they refer to a head being cracked.  I'm positive so far it's valve related from either wrong type lifters or something in that line but the bottom line is when the valves  get hot they lengthen which is normal and that's why having enough valve clearance is important.  Not enough clearance and it forces the valve off the seat enough to let compression leak off.  When it's running it's probably still leaking a little bit but the piston is compressing the air so fast it isn't as noticible and doesn't have enough time to leak off enough for you to notice.  But stop it and  it will not build enough compression till the clearance gets a little bigger or actualy {some clearance period} which sounds like the problem from what I read so far.  A compression test would show it but the time it takes to pull the lines and injectors and hook up the gauge the clearance will probably be back by then and not show up on the test.  I think the 1.9 guys here would know more about the lifters but the valve clearance or lack of some sounds like what's wrong to me, .001 off the seat will cause it to not seal.

[burn_your_money]

With the engine hot, do a voltage drop test on the starting circuit.

[Rabbit TD]

Lets get this clear.  When you say it wont start are you saying it won't crank at all or spin fast enough or just not fire and  cranking fine.  If it won't even crank at all it's probably electrical, if it cranks fine and has fuel it's probably compression {valves off their seat} if it cranks slow it could be anything from a heat soaked starter which I doubt for just a minuet or so to cables, still doubt because the same problem would probably be there when it's cold too.  You did say you had the engine bored, if it's cranking slow it's probably just that the engine is tight yet but will eventualy loosen up after you get some miles on it.  But won't start is a broad description if we're not seeing or hearing it happening. If you have a good temp gauge and your oil pressure is good I'd drive it around and put some miles on it and see if it changes a little.  My 350 in my truck did the same thing after it was bored, after it got a little warm ad you stopped it the engine had tocool down for a little to be able to spinn fast enough to start but it loosened up pretty quick.  We only are supposed to have .001 clearance on these engines between piston and cyl when bored, that's pretty snug and if it's a little less it;s almost guaranteed to slow it down to the no start or even no crank point until it cools down and break in some and if the starter is a little weak or battey too the problems are more compounded.

[stopping]

Mabe just not enough battery for the tight engine .... yes it is tight a thou would be about right. I have another set of batteries that are paired. Should I resolve to have two batteries? Right now the battery is just behind the firewall in the Vanagon and a shorter/fatter wire length than original but the battery is only 600CCamps.
I will be doing a compression test tomorrow.

It cranks.... fast cranking helps.. say when a friend offers me a boost from another diesel ... it did start sooner that the prerequisite 1/2hour. I will do a voltage drop test(good idea). The starter gets hot but I have not pushed it since I burnt it out once completely this week and once by half (one of the two ground brushes un-soldered itself. I turn the com and re-soldered with silver, put grease on the bushings and spray moly on the bedix and all seems to crank well now....just maybe not fast enough.

I am interested in this valve problem.... are there different size hyraulic lifters for these AAZ heads?

[stopping]

There was a significant voltage drop on the battery when starting cold (down to 9v) I think that is a problem. It measured 12.75v before starting and 10.5 after starting... and yes it did start! More voltage reports soon.

I would like to assume for now that this might be a multi faceted problem......

There are two different types of lifters for that year of engine. What is the difference and what problems could result if I have the wrong ones?

[stopping]

Ok here are the results,

The voltage drop when cold was not 9v it was 9.8v lets call it 10v. When cranking the hot engine, voltage drop is just under 11 volts and it does not start.

What is wrong?

There are two different diameters of lifters for this kind of engine....
26mm thick o/d 36mm 93 and less   
26mm thick o/d 35mm 94 and later

Mine are 34.9 (35mm) there is no difference in thickness.... I don't think I have the wrong diameter of lifters since the tolerance is what I would expect...0.05 of oil around the lifters.

Maybe the springs are shot? But again this head is relatively new.

 

[stopping]

I think it is the pump. The pump gets warm and it can't develop the pressure to open the injectors when it is hot. Same thing with the other pump... just so happens I have two tired pumps here (not that surprising).

[burn_your_money]

pour cold water on the head of the pump when it's hot and see if it will start then.

You should do a voltage drop test on the cables as well with the engine hot