ISSPRO Tach?

[91W350]

When I bought my 1991 W250, it came complete with a tripod gauge setup, all ISSPRO, tach, manifold pressure and exhaust temp. I have not towed anything with it yet, but the exhaust temp has never moved. The boost runs up around 18 pounds if you are hanging your leg in it. The tach though, it registers 1900 rpm when the governor shuts down the fuel. The truck will run 90 mph, so I suspect the tach is way off. Does anybody have experience with these or maybe an installation diagram they would be willing to burn a copy of so I can check things out? BTW, it has a Pac Brake that I cannot tell if it is working or not. I have not tried it at high rpm, just mid range down and really could not tell any differnce. Thanks, Glen

 

[NIsaacs]

Some isspro tachs drive off the harmonic balancer and some off the alternator. Some are adjustable, with switches on the back. Check your pyro probe it might be bad or the wiring itself. The Pac brake is not working or you would feel and hear it. Check the vacuum supply and the wiring from the main switch to the throttle switch to the valve solenoid. Also check that if moves freely.





"NICK"

 

[DBF]

Let me just address the exhaust temp, the simplest. One terminal on the gage should have 12vdc on it when the key is in the "run" position, the other terminal goes to the sensor on the exhaust manifold, and through it to ground via the manifold and lots of contacts with the body. The varying resistance in the sensor causes the needle to move on the gage.



If you don't have 12vdc on either terminal, trace the wire toward the power source and fix it. If you have 12vdc at the gage, then the wire going toward the sensor is open (repair it) or the sensor itself is open (replace it).



DBF

 

[NIsaacs]

Some Isspro pyros don't use power, only resistance in ohms. However I am not sure how to check them. Some are very sensitive and hard to trouble shoot.





"NICK'

 

[TKingsbury]

My Isspro has two wires and does not have a power wire. Just two wires that connect the guage to the thermocouple.

Travis. .

 

[JLEONARD]

My pyro also does not have a power wire.

Jay

 

[DBF]

Went out to look at mine again. Turns out it is not an ISSPRO setup, but it has "HI" on the gage label. Looks just like the ISSPRO gages. All my other gages & sensors are ISSPRO, but this one isn't. Now I'm trying to figure out what I have.



DBF

 

[DBF]

Oops. Looked at wrong gage. Pyrometer indeed has no power going to it (just power for the light in it).



Finally found a pyrometer hookup discussion and sample wiring at this link:



http://www.hewittindustries.com/instruments.htm



DBF

 

[91W350]

Thanks guys, a great list of sources to start with. The Pac Brake seems to be frozen, cannot move it all all. I guess the next thing is to take it off and work with it on the bench, a little gentle persuassion maybe? The truck had not been started for two years, rats had found it, so it has probabkly been squirted with a corrosive sort of lubricant. :--) The top of the valve cover plate was just littered with the tattle tale little turds. Glen

 

[Paychk]

The exhaust brake may have been frozen when it was parked, if it wasn't used much, the exhaust brake needs to be cycled on a regular basis or they'll lock up. The Pac Brake that was "Pay forward" to me, was in that condition, no amount of PB Blaster or other penetrants helped. A trip to work with me and a rose bud (heating tip) on the Oxy/natural gas torch freed it up. The housing was glowing a dull red all over; as it cooled slowly, I kept rotating the shaft & dribbling PB Blaster into the bushings.

 

[91W350]

Thanks for the tip, I doubt I would have been nearly aggressive enough.



Maybe this truck used to belong to another TDR member? It is medium almost sky blue with a dark blue stripe, a W 250 from the Englewood Colorado area. I assume the previous owner had horses, when I removed the bed liner, there was a bunch of flat shoe nails under it.



It wound up here in Salina, they were coming through on the Interstate and the Getrag decided it was time to quit. They traded it here for a Duramax I'll bet that made their year!



Anyway, the dealer bought it and used it for a garden and lawn truck at his place in the county. When he got bored with the noise and lack of flash, he replaced it with an H2 Hummer. The W 250 sat back in skid row, "Not for sale" for a couple of years. I saw him at a local club the other night and told him it was time to get the old Cummins running before it rotted away, for the first time in two years he told me to come visit him Tuesday, I was there!



If anybody knows the history, it would be nice know, should have just turned over 200K when the transmission went south. Glen