Testing Compression

[Jetexas]

Thanks to Sailmonkey we were able to prime our injectors and try things again this weekend. However, we found that only one cylinder of the injector pump was pumping. We used the good line off the injector pump to test both the injectors and while both were passing fuel, neither was making good, constant pulses. We also found the solenoid to the glow plugs wasn't working.

Jumpering the glow plugs, we still tried to start it with just the one good cylinder, but we had no luck.

The solenoid, the injectors and the injector pump came home with us to be reworked.

Can anyone suggest a good shop in the Houston/Clear Lake area to rebuild our injectors and pump?

Thanks everyone for your help.

[Jetexas]

I was able to succesfully unsieze and clean the injector pump, but it looks like I'm going to have to turn to a pro on the injectors. Trying to crack those things open actually shattered the jaws of my vice - although it was a cheap vice from Harbor Freight.

My injector pump has two pistons that ride on the camshaft to move them up and down. Since they're spring loaded and default into the down position, I'm assuming that just bolting the pump back down into place is going to move each piston back into it's correct timing. Does this sound right or is it wishful thinking?

[Sailmonkey]

You're good to go there......as far as the injectors, if they were spraying a fine mist without a bunch of dribbling they're also fine. there is nothing you can do at home with these things. The tolerances are measured in microns, not something that can be worked on without a "clean room" and new parts.

I forgot to ask, what do you mean by good constant pulses? Remember these things will only deliver fuel when the engine is ready to burn it, and the amount of fuel they deliver is only going to be a CC or less. I'd guess your engine only burns a quart or so an hour at full throttle......break that up into several thousand injections per hour and you'll begin to get an idea of how much fuel you're looking at.

[Jetexas]

By "good constant pulses" I meant that the injector would squirt hard once or twice, then barely squirt or not squirt a couple times, then it would have another hard one. With the engine cranking at a constant speed, I'm guessing there should be some consitency to the pulses. I didn't actually see it because I was up in the cockpit turning the key and Ben was sitting with a cup under the injector checking the spray patterns, but that's how he described it to me. He said he felt like the nozzles were a bit clogged. The first fuel they blew out was black. By the time we quit testing they were blowing clean diesel, and we did put one back in cylinder 1 and tried a couple more times to start the engine on 1 cylinder, but we had no luck.

When I opened the injection pump and inspected all the cylinders, plungers, etc. I found green algae stains in the cylinder that had been frozen. I soaked it and cleaned it carefully, but I was careful not to brush or sand any pieces for fear of changing tolerances.

I did a major scrubbing on the injector nozzles and let them soak in some carb cleaner, but I'm worried the insides of each injector are all gummed up with algae the same way. I was going to open them, clean the parts and put them back together - but I couldn't get them open.

We're going to retest everything Saturday.

[sigmasailor]

If you manage to open those injectors you will not be able to re-assemble them properly.
You need a special pump with calibrated pressure gauge to re-adjust them. To get a good (metal to metal) seal of the nozzle to the injector body we used to lap the surfaces that connect with lapping paste (very fine, more like polishing).
Not something that could be done without the special tools.

If the engine is not running and at full throttle the pump should deliver the same amount of fuel all the time (hard squirting as you describe it); it shouldn't start to barely squirt. It will throttle back if the engine starts making revs. At starting speeds you should get max fuel all the time. Maybe some air in the system or a hanging fuel pump cilinder.

[cantxsailor]

The guys at Diesel Injector and Pump Service on Navigation in Houston did mine and Everything still works. Give them a call 713 921 2318

[Sailmonkey]

Since the pump was "sticky" i'd suspect that was the culprit for the uneven fuel delivery. The injectors are nothing more than well calibrated pressure relief valves, the only moving parts are the spring and the needle/valve section in the middle.
I would bolt the pump back on now that the plungers are moving freely and try again. I know if that was mine I'd feel better spending money on a complete pump and injector re-build once the engine coughs a bit.

[Jetexas]

If it doesn't at least sputter this weekend, I'm not sure what I'll do. You may see an angry green man throwing it over the stern.

But really, if it comes down to a new pump ($1300) or injectors ($388 each), we'll probably just buy the next used running Yanmar we come across. That's why I went through the pump myself last night instead of immediately taking it to a shop.

[Sailmonkey]

At the very least, an outboard on the stern and a lot of extra storage space inside is a plus.

[Jetexas]

As I was going through the pump again tonight, Ben did say, "Well, it was more like diesel jets coming out of the injectors, it wasn't really atomizing the fuel at all."

I've scrubbed the injector nozzles with a wire brush until the holes can clearly be seen, and they're sitting in carb cleaner. Hopefully we'll get something this weekend.

[SkiprJohn]

Take it easy with the wire brush, those injectors are very sensitive little animals. It really takes a professional to adjust them and recognize how they are supposed to spray. If you don't have a manual it would be good to look for one.
regards,

[Jetexas]

Here's another compression question. If I turn over the engine with the injectors installed but without the fuel lines attached, should the compression of the cylinder be able to blow air up through the injectors?

My injector pump cleanup worked. However, our injectors seem to be shot. One is shooting three watergun sprays & the other is just dripping. We were wondering if the compression of the engine blowing up through them is just further evidence of failure.

[Chief Engineer]

There should be no air coming out of disconnected injectors

[Jetexas]

That's what I suspected.

We don't want to pay for new injectors if we can't verify good compression. However, we can't find an affordable compression tester to fit the motor.

We can turn the motor over by hand, not even using a wrench. We THINK we're losing compression at the injectors because the rings seem good.

If we cap the injectors, and we can still turn it over by hand, should we call it a loss and repower or are we missing something?

A used Volvo is available for $1500 whereas just rings and injectors will cost us around $1000.

[hellosailor]

$388 each for injectors?! Even if that is MSRP, that's highway robbery. Cal that injector shop you were referred to, I'll be a rebuild is no more than $50-75 each and that should be as good as new. There may also be third party injectors available without the "gen-you-whine" price tag of the OEM ones.

Reminds me of the old joke about a kangaroo who goes into a bar and orders a shot of whiskey. The bartender figures, dumb 'roo, what's he know? And charges him $20 for the shot. The kangaroo pays up, and the bartender says "You know, we don't get many kangaroos in here." And the kangaroo says "And at these prices, you won't see many more of us, either."

The injector shop guys may also be able to refer you to a competent diesel mechanic who can come out and shorten the learning curve.