Glow Plug Schematic question

[Tommy dee]

HI guys
I have a Cat 301.7d cr. I have a great wiring schematic. Everything makes sense except the glow plugs. It shows power from the ignition switch directly to the glow plugs and a tap to the glow plug light. No timer or relay. The excavator isn't starting that well. The light only stays on for less than a second. Any ideas.

 

[heymccall]

Schematic sucks

Somewhere along red line is one of these

Found here on machine


It's all automatic.

 

[Tommy dee]

O man....thanks so much. I was going crazy. Now that you pointed out this timer brain box. Is it affected by temperature also.

 

[heymccall]

It is simply a timer. Every engine start, whether hot or stone cold, triggers this timer, which, in turn, activates the glow plugs (and glow plug lamp). Can't find the specs on this particular one, but, the HCO108 is 6 seconds.

 

[Tommy dee]

So this one is turning on for around 1 second. Is it burnt out. The manual says it should be 2 seconds. It never starts on the first or second attempt. I had a takeuchi that was the exact same size. Started first time everytime but the glow plug stayed on much longer. Is there different model timers for the cat with a longer time that I can plug right in?

 

[heymccall]

Are you sure that the problem isn't elsewhere?
All of my Yanmar powered Takeuchi machines do NOT need glow plugs/ preheating to start normal at temperature down to the freezing point. They all require manual preheating, which no one ever does, unless it's darned cold outside.

The lamp working doesn't verify that the preheat is actually working. Have you actually tested the glow plugs?

How many hours on machine?

 

[Tommy dee]

This machine is a cat 301.7dcr . It has 2600 hours. I'm waiting for a nicer day to work on it. The glow plugs look deep in there. From what I can see I have to take the intake manifold off in order to get at them. Little bit of a pain in the ass. I'm going to try and get my probe in there and see how long it says at 12volts. I never had to check the takeuchi because it started so good.

 

[Tommy dee]

So Cat said the glow plugs are controlled from the ECM. Which changes the delay depending on the temperature. Does that mean it's using the engine coolant sensor?

 

[fastline]

The extreme very first thing to do is both determine if glows are firing at all, then determine if one or all of them are bad. That is very simple with a meter and some knowledge. You can look at a GP control until you are blue but if glows are not good, you are SOL. Don't even waste your time pulling them to check, a meter will tell the story.

 

[Tommy dee]

Ok...sounds good. Thanks.

 

[John C.]

All those smaller machines went to an automatic application of the glow plugs and all of them didn't run long enough to allow for the engine to start on cold days. I had tons of issues with them on trade in machines of that time period. I suggested to several customers to find a way to put a manually operated button bridged into the plugs and their problem would be solved. I don't know if anyone did that.

 

[Tommy dee]

The manual says it should stay on for 4 seconds. It barely does one second. The finning guy said it varies on temperature which is controlled by ECM. I think you're right. It's just a preset short delay. I wish there was a proper wiring diagram. I'm gonna buy a extra timer and smash the original open to see how it works. I will put a manual push button though. Definitely would make it easier.

 

[Nige]

So Cat said the glow plugs are controlled from the ECM. Which changes the delay depending on the temperature. Does that mean it's using the engine coolant sensor?

Unless your machine has an ambient temperature sensor on it as well.........
Seeing as you never supplied a Serial Number it's hard to answer.
A quick look at a generic 301.7D reveals that it doesn't have an ECM so I call BS on what Finning told you.

Post the publication reference of the manual you have for your machine please.

 

[Tommy dee]

Cat3017djlj800731

 

[heymccall]

I don't see ECM in here either.

 

[Nige]

Cat3017djlj800731

Confirmed - no ECM.
Attached the starting instructions from the O&M Manual. Take particular note of Step 5.

EDIT: It could be the starting instructions are written around the electrical schematic, so in that case both of them would be wrong.

 

[Tommy dee]

I see the positions but the key only goes to on and then a spring load start position. Why does it show the positions but it won't go there.

 

[Nige]

I see the positions but the key only goes to on and then a spring load start position. Why does it show the positions but it won't go there.

See my reply above. I would opine that the Operator Manual is written on the basis of the schematic which you know is wrong. The schematic shows a key start switch with a 4 positions, OFF, ON, GLOW, & START.

As daft as it sounds maybe the solution would be to get hold of a 4-position key switch, connect Pos 3 of the switch directly to the glow plugs and to the glow plug warning light (as per the schematic), and junk the timer.

 

[Tommy dee]

Ok the outer ring just pops of and it was in the wrong position. Still it only has two spots. But I noticed the spring load spot goes way further to the last position

 

[Tommy dee]

Thanks for the reply. I agree.