Hmm. Compression test.

[86ford69]

I just swung by Harbor Frieght and picked up a compression tester kit. It says it will check rings and valves and late timing. There are a few fittings and Im sure one of them will fit. Problem is the gauge only goes to 300. Im sure I read somewhere that my IDI should be in the 400 range or more. What to do? Dont feel like driving 40 miles back to Harbor Friehgt so can I make this work. Also my buddy has a comp test kit to Ill have to see what his gauge goes to.

 

[icanfixall]

All the diesel compression gauges run up to 1000 lbs. Our engines can make 500 plus pounds of compression so the setup you have will not work... Sorry for the bad news. Sounds like Harbor Freight is telling you this thing will do it all but I have no idea how its going to tell you if a vlave is bad or the rings are bad.... On a gasser... Maybe but not a diesel.... We can't squirt oil down a cylinder to make a better ring seal like you can in a gasser.... Our engines use the oil as fuel....

 

[86ford69]

Thanks man. Looks like Im getting a different gauge from my father law over at GM. I just wanna now if my compression is ok. Im eating like its candy! So if I have some bad rings that should show a low reading right? I had a feeling i shoulds got other kit. Oh welll live and learn.

 

[Diesel JD]

Maybe it will show bad rings and maybe it won't. As Gary said these engines will burn a lot of oil before they will even start to blue smoke. I've been around an IDI that ate 6 quarts per 200 miles and still sounded pretty decent and worked hard every day. Back on the old forum the rule of thumb was that if it burnt more than a quart in 300 or 400 miles it was time for a rebuild but that was lame advice, I think we all know better than that by now. It's time for an overhaul when you want a fresh engine or something breaks or is about too...or it burns so much oil that you are violating smog laws or it's just too expensive to keep feeding it oil. As far as if you just want to know your compression, look for 300 psi and up and the lowest cylinder should be no more than 25% lower than the highest. For example even with your oil consumption you'll probably find at least one 400psi cylinder in there so the lowest shouldn't be below 300. It's a lot of work but I know you're curious, I certainly was, just so I knew what I had. Good luck.

 

[gonecrazyi]

Mine burns a qt every 200 or so miles but it runs great and starts right when you hit the key.

My last motor had around 200 psi on each cylinder and still ran until it lost number 8. It was slow and had no power, but it ran and never left me stranded. The last day she started I made it to work and back home. On the way home she smoked and missed bad and couldn't get over 35, but she made it. Then she never started again, couldnt even get a hit on ether.

I really need to get a good compression guage to check all the motors Ive accumulated. Im curious to see what some of them have.

 

[MidnightBlade]

Be Careful, the Harbor Freight compression testers have the fitting for the 6.9 and 7.3 BUT.... the fitting is longer than the GP hole so it won't thread in or seal.

 

[hce]

Be Careful, the Harbor Freight compression testers have the fitting for the 6.9 and 7.3 BUT.... the fitting is longer than the GP hole so it won't thread in or seal.

x2
i
I used my little lathe and cut fitting, now it works quite well.

 

[Diesel JD]

Mine burns a qt every 200 or so miles but it runs great and starts right when you hit the key.

My last motor had around 200 psi on each cylinder and still ran until it lost number 8. It was slow and had no power, but it ran and never left me stranded. The last day she started I made it to work and back home. On the way home she smoked and missed bad and couldn't get over 35, but she made it. Then she never started again, couldnt even get a hit on ether.

I really need to get a good compression guage to check all the motors Ive accumulated. Im curious to see what some of them have.

Billy I have the Foster gauge and I'd be glad to bring it next time I'm in the area or just let you borrow it. You need to buy or build the glow plug adapter though because I lost mine working on a friend's truck a few years back.

 

[damac]

I got the harbor freight tester and used their fitting along with an old glowplug to tack together something that would thread into the glowplug hole, but had their check valve in the bottom like the other fittings in the kit.

It seems to have worked, I got pretty much the same readings after multiple tries.

 

[gonecrazyi]

I have access to a tester with the adapter but th guage doenst work properly. Id love to borrow when your down this way. Odd you go over to juniors to do his timing let me know and i'll shoot up that way.

 

[86ford69]

Well I'm gunna check it out today and see what happens. One more thing. I've heard of a couple different ways to do the test. 1 is to remove all plugs and crank the motor for 8 to 10 seconds on each cylinder. 2 is to just remove one plug and fire it up. I do know the engine has to be warm. Also gunna check with my neighbor to see what his gauge goes to.

 

[GOOSE]

I spent the twenty some bucks on a HF tester. The next day I spent the $125 for a good one at a reputable paarts store. Don't get me started on HF again.

 

[86ford69]

What to do?

 

[icanfixall]

Do not start the engine and try to do a compression test. Your guge will blow apart... Who told you that its possible to do a comp test that way..... Its not going to tell you anything and its dangerous. Please remove all the glow plugs and test each cylinder as you go. Pull the wires off the top of the injection pump so there is no chance of the engine starting. Don't squirt any oil into the cylinders either like we do in the gasser engines. Write down all the pressures too. It helps when reading what cylinders may have issues between each other.

 

[86ford69]

Ok I thought that was the right way but some dude told me to start it and that just sounded crazy. Still need a bigger gauge. Mine only goes to 300!