1982 DIESEL PL 720 Pickup

Glow plug relay or the engine is tired and needs a double shot of glow plug heat to fire off. How does it crank when it's warm?

Reply to
Steve T
Loading thread data ...

I'm hoping for some assistance with a 1982 PL720 Pickup .... with

22SD diesel engine. Occasion, the engine cranks over just fine but won't start running. The "workaround" is to release the key from START, quickly turn the key all the way back to OFF and then back to START. Again the engine will crank like crazy and then quickly catch and run ... like nothing odd happened. Any ideas?

The next question will be about exhaust smoke but lets deal with the above first. Thanks! :^)

Reply to
Philip®

On Fri, 20 Feb 2004 05:15:48 GMT, "Philip®" wrote with a sharpened banana:

sounds like faulty glow plugs to me, test all 4 glow plugs with an ohmmeter, they should be less than 1 ohm each, while you're at it test compressions regards

Andrew Clark All Round Car Guy

Reply to
Johnny B Goode

Steve: Thank you for responding. The engine ALWAYS cranks over fast. It's the crank and -catch- part. This problem almost always cures itself if the truck is left to sit and cool off. In other words, the problem usually manifests after shutting the engine down ... letting it sit for less than a half hour ... and then trying to restart.

The glow plug light always comes ON with the ignition key and goes out (with a click) in about 45-60 seconds. I usually wait about 20 seconds on a cold engine before cranking it up. But does this engine need hot glow plugs to start a hot engine? Once the engine cranks and fires off, it idles just fine, no unusual mechanical knocks, and has decent power .... for a 61 horsepower naturally aspirated diesel (LOL).

Steve, you mentioned a glow plug relay. In studying what harnesses go where, there is a black box (5x4") mounted on the fender well next to the main fuel filter with two short harnesses coming out of it that lead to a servo motor (?) on the side of the engine which has linkage leading to the fuel injection pump. Is this the 'relay' you're referring to? There is also another little "solenoid" right next to this black "relay" box in question

The engine/truck has 125k miles on it, never been overheated. The original owner tells me the oil has always turned black in a very short period of time. Engine oil services have been on the order of

3-4k miles. I checked and adjusted the valves ("overhead adjustment") to .35mm. None was more than .05mm off.

Thank you.

Reply to
Philip®

In news: snipped-for-privacy@4ax.com, Johnny B Goode being of bellicose mind posted:

All four glow plugs have 1 ohm resistance. This is an all or nothing failure to 'catch and run' ... hot or cold. How would a compression test be helpful in diagnosing? When the engine is running, there is a steady flow from the exhaust (no puffing like a misfire) but the little bugger CAN spew a huge continual smoke cloud on long hard hills (ie, full throttle in 3rd gear @ 38 mph).

Thanks for your input.

Reply to
Philip®

On Fri, 20 Feb 2004 18:13:48 GMT, "Philip®" wrote with a sharpened banana:

ok then your motor obviously has the inline type injector pump with the stepping motor unit connected to the back, there is a control relay that operates this motor and I have seen them fail before, basically there is a start position (fully in) a stop position (fully out) and a run position (in between) check that this motor is doing it's thing when you turn the key on. other than that I would need tom be there to "get the hands dirty" to really get a handle on the problem

Reply to
Johnny B Goode

I assumed this was a cold start problem. BTW starting a diesel before the glow plugs "turn off" is a bad idea. Blowing fuel across hot glow plugs can burn them up. I'm not that fluent with diesels but did work at a benz shop for a while and learned a little about them. I drove one of those nissan diesel pickups for about 6 months and yes, they are slow!

Reply to
Steve T

In news: snipped-for-privacy@4ax.com, Johnny B Goode being of bellicose mind posted:

Hehehhee. This one is a little different. A "windshield motor" thing IS present but not on the back of the injection pump. This one has that "windshield motor" looking thing (stepper motor?) mounted down low, below the injection pump with a linkage rod going up to the a lever on the side of the injection pump. The "stepper motor" does have a 7 pin connector, connecting to a harness that leads up to a black box on the fender. This is the control relay? With another person turning the ignition key to ON does not make the stepper motor react at all. But turning the key to START does make it move full up while starting (but not always ... hence the No Start condition??) for the duration of starting and then it repositions again ... engine still running. Full down position is where it goes when the engine is not running. Never had a problem shutting the engine OFF.

I'm getting the impression that the problem is with this control box or the ignition switch itself?

Thank you.

Reply to
Philip®

On Sat, 21 Feb 2004 03:21:10 GMT, "Philip®" wrote with a sharpened banana:

yes it sounds like the right track, the gray matter is getting old now remembering these old things, sometimes opening up the control relay and re soldering the connections to the circuit board inside can help as the vibration gets to them after a few years or you can revert to the system in the early 620 series trucks that used a hand operated cable (push to start and pull to shut down) cheers

Andrew Clark All Round Car Guy

Reply to
Johnny B Goode

Steve: "Starting before the glow plugs turn OFF is a bad idea?" Huh? That would mean (a) I'd have to wait for about a minute before cranking a cold engine and (b) I would have precious seconds while the glow plugs were still hot to get the engine started. As is, the glow plug lamp turns off the second the engine fires off and the ignition key is released from START to ON. I think you're on to something with either the control relay box or the ignition switch itself. I'm confident the ignition switch can be purchased but .. the control relay? And for how much $$? Wrecking yard time perhaps.

Yeah, this thing is S_L_O_W. But having driven line haul for 12 years, slow is something you just get used to (meaning ... never ever give up momentum!).

Next item: The smoke. This thing on occasion can produce a continual charcoal cloud that would rival a million mile, worn out Cummins. There's no reliable rhyme or reason to the occurrence other than full throttle. Sometimes it even smokes while coasting down hill! Oil consumption isn't bad ... 2500+ miles to a quart (so the previous owner tells me). Ya think injectors or injection pump?

Thanks again!

Reply to
Philip®

In news: snipped-for-privacy@4ax.com, Johnny B Goode being of bellicose mind posted:

Hmmm. THERE's an idea. I'll see if I can remove the top cover from the control relay and inspect/solder any faulty connections. I'm not keen on a manual shut down cable ... but I do know what you're referring to. Thanks!

Reply to
Philip®

Have you read the manual? The plugs are suposed to heat up the head not supply a glowing "ember" to lite the fuel off. That's why it stays on longer when the engine is cold. If it was just there to ignite the fuel, you wouldn't need to wait at all.

Reply to
Steve T

mp goes out every time,

Another tip in -really- cold weather is let the glow plugs cycle twice before cranking. The one I drove needed this on really cold mornings.

Reply to
Steve T

(Walks out to the truck to retrieve the tattered Owner's Manual ... thumbs thru to "start up procedure.")

Hmmmm! You're right! It says turn the key to ON and wait until the glow plug light extinguishes ... then crank with the throttle fully depressed. You wait until the glow plug lamp goes out every time, regardless of engine temperature. Ok.

There is a special note about starting a cold engine in COLD weather. Paraphrased: As soon as the glow plug light goes out, IMMEDIATELY crank the engine or it may not start.

All "starts" are made with the throttle fully depressed while cranking. Yep, this is a bit different starting drill than the semis I used to drive.

Guess I better do something about the glow plug light because it is hard to see when it's ON during daylight. A bit dim compaired to other red indicatior lamps at night too.

Reply to
Philip®

Steve: I got into the instrument cluster today ... couple of burned out bulbs. I also had the top cover off the steering colum to look at the ignition switch. SURE ENOUGH ... the plastic part containing the contacts was quite loose in the metal housing! So I took the switch out and used a very small pin punch to tighten up the 3 peen-over points that hold the plastic part into the housing. I did this only because (a) I could not find a new switch and (b) the switch I did find was not like the one in the truck. Mine turned out to have a different orientation than the catalogues called out for. In fact, after looking thru the picture section of a switch catalogue at AutoZone, the correct switch appears to be one for a Subaru

1977-1981. What the hay? Don't know yet if THIS fixes the occaisional failure to 'catch' problem but I'll know soon.
Reply to
Philip®

Being in southern California and a bit inland from the ocean .... I'm not apt to experience "really cold" weather. When we've stayed in Bridgeport, the overnight lows have been down to 5 degrees during the winter lately. But I'll never drive this truck up there! LOL.

Reply to
Philip®

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.