Wait Light on Momentarily

[tgtaylor64]

When I turn the key, the wait light comes on for about 2-3 seconds. Looking at the voltage gauge I can see that the plugs are warming. After about 15 seconds (depending on temp, etc.), I know to listen for the relay to open and the gauge to rise, signaling that the glow plug cycle has completed and it is now OK to hit the starter to crank the M1009. It always starts. I have a new GP card and GP relay. My question is: why does the wait light not stay on for the entire initial GP warming time?

 

[tstone]

The design intends that the engine be cranked for a few seconds while the glow plugs are still activated.

 

[doghead]

I think this is a good question for Karl or John to answer.

 

[antennaclimber]

tstone is correct.

Without getting in to the electrical design of the GP controller. Here is a simple answer:

The wait light comes on for a shorter duration that the GP heat time.
This is the way the GP card is designed to function.

I am assuming that the designers of the engine wanted the GP heat time to be long enough to start the engine, then with the colder air being pulled in to the engine immediately after start up , the controller card keeps the GP's on until the engine has developed enough heat to allow for it to run as designed. This time is called after glow or refire.

I would recommend that as soon as the wait light goes out, that you start to crank the engine to get some air moving and keep the GP's from possible damage.

I hope this helps.
Karl

 

[tgtaylor64]

It will not start after this 2-3 second wait delay. The wait light comes on for this time regardless of ambient and/or engine temperature. Could it be a bad temp sending sensor?

 

[mistaken1]

Sounds like its time for this:

 

[txmytx_catahoula]

After I did the doghead conversion I had a problem with the Wait light illuminating for just a second or two. I figured it was a grounding problem so this last weekend I got out the pencil erasers and electrical contact cleaner and cleaned the connections at the firewall, the connector for the wait light/ glow plug system under the dash and the controller card. Everything is working sweet now. The cold front this week should be the true test.

 

[combatmech]

Mine does it as well from time to time. Seems to only happen when outside air temps are above 70F or the truck has been running for a while. It did get a little cooler over the weekend, wait light stayed on a little longer....system worked as advertised.

 

[1stSarge]

This could be a lot of things. I agree with what has been suggested before but here are a few more things to ponder;

The simple answer is there could be a problem with the controller. I say this because I have seen this very thing in repairing controllers, and the problem was a resistor that was way out of tolerance, replacing that resistor corrected the problem.

The wait time is almost always around half of what the relay time is so the 2-3 second - 15 seconds ratio does not sound right to me.

Another idea, is that there may be some other mechanical problem, like fuel or just wear and tear on the engine.

Both the wait light time and the relay time operate off of the temp sensor, so it is unlikely that it is the culprit.

Finally, there could be bad plugs, check the resistance on each one. The procedure is outlined in the troubleshooting section of the TM that mistaken posted. At least 1 ohm and no more that 3 ohms.

Let us know

 

[tgtaylor64]

Problem solved! Normally, the WAIT light is on the left and the WATER IN FUEL light is on the right. Someone switched the lens. Since the bulb leads are different sizes, the WAIT lead is larger, the WAIT lead was on the WATER IN FUEL side. The bulb was burned out. The WATER lead was on the WAIT side and was, get this, operating as designed. It came on for 2-3 seconds upon start-up! I switched the lens so the holes would accept the correct feed, replaced the bulb and now it works perfectly. He-haw.

 

[ssdvc]

Talk about messin' with your head !!! Somebody was screwin' with someone in the motor pool !!!!!!!!!