1HDFT compression test results (1 Viewer)

[Loober]

Hey all you engine gurus out there.

I've been chasing down sever smoking at startup issue on my 1HDFT. Truck smokes heavily at startup, with thick grey/white smoke that reeks of unburnt fuel. It is especially bad in cool weather and at elevation, and as the truck warms up it subsides to "normal" levels. I must add the truck runs great besides that, no other ill symptoms.

I started with injectors, which checked out to be fine and moved on the to a compression test, where I received some potentially troubling results.

FSM calls for a 498psi, with a low of 350. Mine came in at 410/420 consistently across all cylinders.

Now I did have the head rebuilt not too long ago, I did not follow the FSM procedures to determining the exact head gasket thickness according to the piston protrusion, etc. instead just used the thickest #5 gasket, which was recommended at the time. So it could be that I used too thick of gasket therefore lower the compression on the engine?

What do you all think of those results? Its within the allowable range, but a little concerning that its not closer to optimum.

Could the lower compression be causing the smoking issues I am having? Further exaggerated with cold air causing incomplete combustion until the air warms up?

Also note, I do not have the glow screen hooked up and ACSD deleted, but with comparisons to others who have done that as well on the same engine, with no smoke. Makes me think those should not have much effect on my situation.

My timing was advanced towards the top of the range, I am going to retard it, see if that helps.

 

[chapel gate]

whilst we all want our compression readings to be as high as possible. they are not concerning and are consistent.

low compression due to worn rings/bores would show blue smoke all the time.

 

[Loober]

@chapel gate thanks, I kind of thought the same, nice to hear it confirmed. Even though not detrimental could it have an effect on the excessive smoking, due to less then optimal combustion caused by lower compression? I am hoping retarding the timing will somewhat counter that?

 

[KiwiDingo]

@chapel gate thanks, I kind of thought the same, nice to hear it confirmed. Even though not detrimental could it have an effect on the excessive smoking, due to less then optimal combustion caused by lower compression? I am hoping retarding the timing will somewhat counter that?

Retarding the timing will do the opposite and make it worse.

 

[Loober]

Is that right? I thought it would allow the combustion to be delayed to take place when cylinder temps are hotter

 

[GTSSportCoupe]

Keep in mind compression testers can vary quite a bit. A long hose before check valve in the tester effectively adds volume to the cylinder and will lower the reading for example. I bet your compression is just fine. Most engine's I've seen with bad compression issues vary a lot from cylinder to cylinder.

If the smoke is grey/white it's almost certainly diesel smoke from poor combustion. Very likely related to fuel system tuning.

Diesels usually advance injection timing when cold, which makes starting easier and cleaner. Retarded injection timing could definitely cause issues for cold start. The ECD diesels (1HDFTE for example) will retard timing when intake air temps get hot to lower cylinder peak pressures (much like gas motors).

 

[Feistl]

As above, I have found compression testing petrol engines to be pretty accurate but on numerous Diesel engines I get significantly lower numbers (on known good condition engines). That level of consistency is a good sign....

Spend the $80 to buy a tool to check the timing. It doesn’t take too long and is worth doing regardless, as the pumps wear they lose timing which can cause some issues. Even if it doesn’t fix your specific issue it’s worth doing considering the cost

 

[Loober]

Thanks for everyone's input. I did time it multiple times using the tool, I had it set at the top of the range per FSM at about 1.55. So I am just at a loss now thats why I started checking compression. I get now that retarding will do the opposite. So what are my options, advance it even more beyond the spec and see what happens? Even when warmed up the truck is noticeably over fueled, does not smoke much but has a ripe fuel scent for those behind me to enjoy. Is it something internal to the pump, should I get that checked out? Hate throwing parts at it without any rhyme or reason though.

 

[GTSSportCoupe]

Thanks for everyone's input. I did time it multiple times using the tool, I had it set at the top of the range per FSM at about 1.55. So I am just at a loss now thats why I started checking compression. I get now that retarding will do the opposite. So what are my options, advance it even more beyond the spec and see what happens? Even when warmed up the truck is noticeably over fueled, does not smoke much but has a ripe fuel scent for those behind me to enjoy. Is it something internal to the pump, should I get that checked out? Hate throwing parts at it without any rhyme or reason though.

Is there a working glow screen or whatever pre-heat system the 1HDFT has?

Have you (or someone else) ever messed with the main fuel screw?

I've timed pumps by ear/performance before - but on IDI. They get pretty rattily and gutless when too advanced. Not sure I'd take the chance on a 1HDFT though, haha.

 

[Loober]

It does have a glow screen, which is not hooked up, all I have read says its only needed in freezing temps, I am dealing with Socal weather here, and it does this even at 50F. rather find the real cause then just find a work around.

 

[KiwiDingo]

This is the biggest issue I have with using the tool to set timing. People focus on what number they are getting instead of looking at what the engine is actually doing and how its performance is changing with each adjustment. Engines, injector pumps, injectors etc all wear and even get replaced with components that are no longer identical to factory so factory spec timing is really just a guide. Even the type of diesel you're using with varying cetane ratings can change massively from one country to another which effects what timing you need for optimum.

 

[SNLC]

I find the more boost or higher elevation increase the timing. Even in the NA engine they seem to like a bit more advanced.

@Loober I would be looking at the fuel system for air leaks. If all good and injectors tested and good I would look at the IP.

Your compressor is fine, not a new engine but fine. As mentioned bad rings and it will smoke blue.

Cheers

 

[Loober]

@KiwiDingo @SNLC that makes sense, with an older engine, the FSM specs may not be ideal for it, so I will play around with the timing see if it gets any better advanced, and go from there.

 

[AussieHJCruza]

From my records, euro spec for timing is 1.52-1.58mm lift and Aussie spec is 1.37-1.43mm.

As @KiwiDingo says and from my experience, as the pump wears with milage, the tolerances change in the pump and it would be worth a bit of a play with the timing. I'd expect it to get very rattly before the timing is over advanced enough to hurt it.

Also, sorry to be this guy but please remember you are working with a mechanical diesel that doesn't have a cat, dpf or any of that sort of thing. It isn't likely to start without a bit of smoke and will always smell 'diesely' unlike a modern common rail engine that's choked with emissions stuff.