Problem starting 6.5 TD engine in Hummer H1 1997 Hi, I have a H1 1997, i was changing the Injectors caps, and when the car came back it was suffering from late starting.. in the beginning it was starting well when cold, and not starting at all when hot (until i spray any flammable material in the air intake), now it doesnt start cold or warm !! ..... I have tried almost everything, Changed Lift pump, changed glow plugs, changed OPS, changed the PMD on the IP, made sure batteries are OK, made sure batteries connections are fine, cleaned up the diesel lines IP is relatively new, injectors were recently maintained, a water separator was also installed 6 months back.. One comment that can be relevant, the car gets overly hot now when driving, that i why i changed PMD, i thought i got bad with the heat in the engine bay. I am stranded, no one seems to know what could be wrong over here, only 1 guy thinks it could be the engine losing internal necessary compression pressure by normal wear!! Really appreciate your help ..

Thanks a lot John, but what tools are needed to test these sensors ? , any idea how can i do this myself ? Thanks a lot John, but what tools are needed to test these sensors ? , any idea how can i do this myself ?

Yes, an ohm meter is all you really need. Isolate the leads tot he sensor(s) themself, it should be 3 leads, but if 2 that is okay. Essentially you check fbetween the three leads with test leads to determine which combinations give you the same reading or similar reading with one wire being common to the negative lead of the test meter. This would be the Base lead of the HE transistor. It should read anywhere from 5000 ohms to 50,000 ohms. With leads reversed, so the red test lead is now on that base lead, The resistance should be about 4 times higher to 10 times higher than the first reading. This woulld be a sensor that is "ok". If the resistance is infinite for any of the measurements, the sensor is bad. The same will be true if the resistance is the same regardless of orientation of test leads to transistor leads. The last part of the check on the 3 wire type is between the two leads that were tested in relation to the Base lead. (With a 2 lead type this is going to be the same general results) You should see about 20 ,000 to 50thousand ohms one way and then the other way should give a different resistance on the order of at least 2 (either half of the first reading, or twice that of the first reading.) If it is the same resistance both ways, replacement is a really good idea because the sensor will be prone to give spurious results, and not trip an error code in the engine computer. Yes, an ohm meter is all you really need. Isolate the leads tot he sensor(s) themself, it should be 3 leads, but if 2 that is okay. Essentially you check fbetween the three leads with test leads to determine which combinations give you the same reading or similar reading with one wire being common to the negative lead of the test meter. This would be the Base lead of the HE transistor. It should read anywhere from 5000 ohms to 50,000 ohms. With leads reversed, so the red test lead is now on that base lead, The resistance should be about 4 times higher to 10 times higher than the first reading. This woulld be a sensor that is "ok". If the resistance is infinite for any of the measurements, the sensor is bad. The same will be true if the resistance is the same regardless of orientation of test leads to transistor leads. The last part of the check on the 3 wire type is between the two leads that were tested in relation to the Base lead. (With a 2 lead type this is going to be the same general results) You should see about 20 ,000 to 50thousand ohms one way and then the other way should give a different resistance on the order of at least 2 (either half of the first reading, or twice that of the first reading.) If it is the same resistance both ways, replacement is a really good idea because the sensor will be prone to give spurious results, and not trip an error code in the engine computer.