Author Topic: Cold Compression Numbers? (Read 3052 times)

drrtybyl · « **on:** January 12, 2009, 06:18:10 pm »

I decided to do a compression test on my 1.5NA due to cold starting trouble and unburned fuel smoke. Here are the numbers I got:

1-295 2-295 3-300 4-205

I'm thinking my unburnt fuel issue is related to cylinder 4. I know warm/hot starting values should be 400+; does anyone have an idea of what cold compression numbers should be? Thanks

boosted_diesel_84 · « **Reply #1 on:** January 12, 2009, 06:30:23 pm »

did u only do it once per cyl? and did u have a charger hooked up to battery?

drrtybyl · « **Reply #2 on:** January 12, 2009, 07:23:29 pm »

The battery was fully charged. Engine was completely cold with fuel shutoff solenoid disconnected in ~45-50F weather . 8 cranking cycles as suggested per the kit.

Smokey Eddy · « **Reply #3 on:** January 12, 2009, 07:54:33 pm »

Vincent Waldon · « **Reply #4 on:** January 12, 2009, 07:58:48 pm »

Warm might be slightly higher, but this is probably an apt test because this is what your diesel is trying to start using. :cry:

drrtybyl · « **Reply #5 on:** January 12, 2009, 08:14:30 pm »

Thanks for the comments.

This test has confirmed what has long been suspected. Looks like an overhaul is in order after all!

drrtybyl · « **Reply #6 on:** January 16, 2009, 11:01:52 am »

Should I stick with this engine or pony up and put together/replace it with a 1.9? There's a place nearby that has several of them in various states.. I'm looking for a fun/reliable DD here that will last a while.

jtanguay · « **Reply #7 on:** January 16, 2009, 11:48:52 am »

Quote from: "drrtybyl"

Should I stick with this engine or pony up and put together/replace it with a 1.9? There's a place nearby that has several of them in various states.. I'm looking for a fun/reliable DD here that will last a while.

i would recommend going with a 1.9 if you have the money. it might be a little overkill for your rabbit though :lol: you might start wanting to tow things with it... :twisted:

you could probably refresh your 1.5 on the cheap though. it all depends on just how worn out the motor really is...

Rabbit TD · « **Reply #8 on:** January 16, 2009, 03:49:30 pm »

The 1.9 would proably be pretty decent in the rabbit, you might not even need first gear :lol: If you can get one that doesn't need rebuilt for a fair price I think that is what I'd do and you have some spare parts that way if you keep the old engine. Probably get pretty good fuel milage out of it too in the Bunny. Maby if one of the 1.9's needs rebuilt you could get it real cheap, I don't think stuff is much more expensive if any on those engines, if I was going to rebuild one and had a choice I would rebuild a 1.9.

jtanguay · « **Reply #9 on:** January 16, 2009, 04:43:28 pm »

1.9 + tdi box + vw rabbit = 60+mpg (with a good runningmotor/calibrated pump)

drrtybyl · « **Reply #10 on:** January 16, 2009, 10:31:12 pm »

Quote from: "jtanguay"

1.9 + tdi box + vw rabbit = 60+mpg (with a good runningmotor/calibrated pump)

Does this estimate consider use of a 5 speed transmission?

I'm just about sold on this idea now even if things look OK when I take it apart tomorrow, heh.

Rabbit TD · « **Reply #11 on:** January 17, 2009, 07:57:43 pm »

Quote from: "jtanguay"

1.9 + tdi box + vw rabbit = 60+mpg (with a good runningmotor/calibrated pump)

That's got a Toyota Prius beat and a whole lot cheaper, less complicated and more fun, I get a kick out of driving beside them on the interstate with my little 81 Rabbit which is the oldest car on there everyday from the ones I see and they look at you like what the hell is that thing. But then you realize you've got less than $2,500 in yours nd they have $25,000 in their's and youre running cheaper than they are :lol: I work with some people that have them.

drrtybyl · « **Reply #12 on:** January 19, 2009, 08:38:33 pm »

Ran compression again using a different adapter/connector (the one specified by the kit -- DOH!) on a slightly warmer day and got these numbers:
1-375 2-395 3-400 4-300
Much better numbers (considering air wasn't leaking from the fitting as before), however cylinder 4 is still looking like the cause of my unburned fuel.

I'm guessing "good" cold compression readings would probably still be right around 400 or higher?