diesel techs input wanted

[Zulfiqar]

What can cause air backdrafting in an IDI diesel intake manifold.

Engine is a toyota 2C diesel 2.0l 4 cyl IDI with VE pump

Problem: air being pushed out the inlet manifold whilst running, its even pushing it beyond the air filter element and out of the inlet snorkel, Engine is 60,000 miles old since factory install with mobil1 diesel used all its life. The motor has great compression on 3 cylinders and a little odd in 1 cylinder, doesnt have gasket probs or starting problems,  But its blowing black now (brainfartingly is due to air not being sucked into the cylinders) EGT climbs to 1000 really easily on full pedal.

Any inputs guys, I used to have this prob on my VW but after fixing the timing it went away - out of time my VW diesel used to murder my battery - This engine starts first key

[maxfax]

Well, I'm by no means a diesel tech in the sense that I had proper shooling on the subject but,

With the other symptoms, and the low compression on one cylinder tells me that you may have an intake valve leaking..

Could just be adjustment, or a broken spring to a bent or burned valve..   An easy check would be to put the questionable cylinder on top dead center and put some compressed air to the cylinder.. (I modified an old compression gauge to connect to an air compressor for this)  Or pop the valve cover and have a look see..


Good luck!

[zukgod1]

What are your compression #'s?

I had one of those 2.0 Toy trucks. Added a Turbo kit and a brand new Turbo pump.
Was a blast compared to NA mode.

I don't have much info here but the only option is an intake valve

[Zulfiqar]

compression is 480 psi on 3 holes and 440 psi in one, it has mech lifters - the low comp cylinder builds pressure a little slow

btw the motor has slight air huffing blowby, from the breather pipe

[jtanguay]

compression is 480 psi on 3 holes and 440 psi in one, it has mech lifters - the low comp cylinder builds pressure a little slow

btw the motor has slight air huffing blowby, from the breather pipe

check the valve lash. more than likely you'll need to adjust them.

[jettabrendan]

Air sounds like a knackered valve.

[Baron VonZeppelin]

I only work on old high mileage VW mostly. Went to school at the University of Vortex Diesel, continuing education here at GTD Institute, and spent many years at the highly accredited School of Hard Knocks and Busted Knuckles.
 
But have noticed at idle these things tend to huff some air pulses back out through the air intake hose. But only at idle/low speed.

Was discovered by accident first time on a car with no known issues.
Was just doing some minor incidentals for a friend.
Checked my 89 NA Hydra and same thing.

Both of those smooth out and symptom seems vanished by 1500 rpm or so.
But they are not low mileage engines.

The numbers seem too good to be anything severe.
But would check both valve lash tolerances on that low cylinder - one may be a little too tight.

If no issue there, try a pure ATF fuel run treatment. Maybe a valve stem to valve guide issue from some carbon or something causing a little sticky'ness. Or a piston ring that needs a little more help getting its rotation back in order.

cheap efforts to try.

just internet type suggestions, fwiw

[jtanguay]

I only work on old high mileage VW mostly. Went to school at the University of Vortex Diesel, continuing education here at GTD Institute, and spent many years at the highly accredited School of Hard Knocks and Busted Knuckles.
 
But have noticed at idle these things tend to huff some air pulses back out through the air intake hose. But only at idle/low speed.

Was discovered by accident first time on a car with no known issues.
Was just doing some minor incidentals for a friend.
Checked my 89 NA Hydra and same thing.

Both of those smooth out and symptom seems vanished by 1500 rpm or so.
But they are not low mileage engines.

hmm you make a good point. older engines with sloppy cylinders do emit blowby gases into the oil pan area (that diminish during high rpms, but magnified at low rpms and high load situations), and could easily back flow to cylinders on the intake stroke. this is just one more reason for having the sump vent system that 1.9 engines have.

[Baron VonZeppelin]

You probly have a tighter grip on it than i would jtang.

I had wondered if it was maybe common due to no throttle valve/ no butterfly blades/ or true vacuum creation/ of our machines.

Its a freaky lil thing when you first notice it.
No fumes or colors come out, just reverse air pulses.

But could be from the miles and wear for all i know.
Wondered if that was what Zulf was experiencing.

[Zulfiqar]

I think a T belt inspection and valve clearance adjustment is in order for that engine, I know that my then NA VW diesel blowed air from the air filter with slightly bad valve timing, but then when adjusted tried to suck the flesh off my hand - If I tried to plug the inlet with it.

This toyota engine pushes my hand away when I block the inlet manifold and dies after 20 or 50 revs if I force it on.

Its also returning a stupid 22mpg in a 1100 Kg car - Normally it gives out at least 35 - 38 mpg when new.

[maxfax]

Sounds like a good place to start..  Since that one cylinder isn;t crazy low on compression valve adjustment  and timing may juse cure your ills..

[jtanguay]

I think a T belt inspection and valve clearance adjustment is in order for that engine, I know that my then NA VW diesel blowed air from the air filter with slightly bad valve timing, but then when adjusted tried to suck the flesh off my hand - If I tried to plug the inlet with it.

This toyota engine pushes my hand away when I block the inlet manifold and dies after 20 or 50 revs if I force it on.

Its also returning a stupid 22mpg in a 1100 Kg car - Normally it gives out at least 35 - 38 mpg when new.

bad mpg is normal for a car that needs valve adjustment. if the valve adjustment gets bad enough, the engine won't even run! of course there isn't much you can do (aside from tearing it down) if the rings are the problem.  if the valves are within spec, then a leakdown test might be in order.  theres a few products that claim to free sticky rings, and that might get you by for a little bit if that is the problem.

[Zulfiqar]

solved.

valve clearances were the problem - stupidly tiny, normal specs were 0.2mm exhaust 0.18mm inlet says the sticker on the valve cover. both IE valves were 0.05mm.. talk about tight, T belt was replaced too, was the original factory part. Now it sounds much better and breathes normal.

[Baron VonZeppelin]

Good job Zulf .

Should be a happy customer on the other end.

[Zulfiqar]

Thinking of going commercial with all these things I have done  - great experience when you do it by hand.