Pre Heat controls for 8.3

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Pre Heat controls for 8.3

October 20, 2012, 11:30:05 am

I am having a problem on cold start until engion is at running temp.

My preheat solenoid is not operating. Does any one know what controls the pre heater and pre heat solenoid?

Re: Pre Heat controls for 8.3

Reply #1 – October 20, 2012, 11:45:44 am

I don't believe that a solenoid is involved in the pre-heat system. It is, as far as I know, just an switched AC outlet in the engine compartment controlled by a switch on the street side foot end base of the bed. There is a cord that is plugged into that outlet and terminates in a connector which is plugged directly into the heating element which is screwed into the head or block up around the alternator area. It can be difficult to see where the element is when the cord is unplugged as it was and is in our 99' U270. I assume it was unplugged because of a problem since outlet end of the cord is slightly melted.
Don

Re: Pre Heat controls for 8.3

Reply #2 – October 20, 2012, 11:56:24 am

Don,

Suspect we are talking about two different things.

Yes, the BLOCK HEATER is 120 VAC and controlled by a switch at the foot of the bed.

The engine INTAKE MANIFOLD HEATER is solenoid controlled.

As with any other solenoid, check for 12 VDC to one of the large lugs (that would be from battery).

Next, check for 12 VDC positive to one of (or the only) small terminal when the engine is cold and key turned on. If that happens, the solenoid should put 12 VDC positive to the other large lug. If not, replace the solenoid. If no power to the small positive terminal, more troubleshooting is required.

Re: Pre Heat controls for 8.3

Reply #3 – October 20, 2012, 12:24:40 pm

I am not getting 12volts to solenoid. I can energize solenoid with 12volts.
I can energize intake heaters by shorting two poles together on relay on wall at foot of bed.

I do not know what triggers the preheater and solenoid. Thermostat?

Larry Bradley
1998 u 270

Re: Pre Heat controls for 8.3

Reply #4 – October 20, 2012, 01:17:25 pm

Man I still have a lot to learn about these coaches! I am sure when we actually start using the coach I will have a lot of learning yet to do! I thought that the pre heat systems were either block heaters like on oour ISC, or the diesel variety when equipped with Aqua-Hot. Is this also called an electric grid heater? And I gather its purpose is to preheat intake air in cold temps...
Don

Quote from: wolfe10 – October 20, 2012, 11:56:24 am

Don,

Suspect we are talking about two different things.

Yes, the BLOCK HEATER is 120 VAC and controlled by a switch at the foot of the bed.

The engine INTAKE MANIFOLD HEATER is solenoid controlled.

As with any other solenoid, check for 12 VDC to one of the large lugs (that would be from battery).

Next, check for 12 VDC positive to one of (or the only) small terminal when the engine is cold and key turned on. If that happens, the solenoid should put 12 VDC positive to the other large lug. If not, replace the solenoid. If no power to the small positive terminal, more troubleshooting is required.

Re: Pre Heat controls for 8.3

Reply #5 – October 20, 2012, 02:45:23 pm

Quote from: wolfe10 – October 20, 2012, 11:56:24 am

Don,

Suspect we are talking about two different things.

Yes, the BLOCK HEATER is 120 VAC and controlled by a switch at the foot of the bed.

Here is some additional Block Heater information.
Block Heater

Re: Pre Heat controls for 8.3

Reply #6 – October 20, 2012, 03:36:20 pm

Thanks for the link, not to mention the page! It would have save me some head scratching had I seen this before I tried to figure out where that loose cord was supposed to be pluged in on the engine...
Don

Quote from: Barry Beam – October 20, 2012, 02:45:23 pm

Here is some additional Block Heater information.
Block Heater

Re: Pre Heat controls for 8.3

Reply #7 – October 20, 2012, 06:02:41 pm

Don,

Block heaters and aqua hots (or clones) are used to warm the block before attempting to start the engine.

The intake manifold grid heater is part of the start process, and is activated by the ignition key.

As to what should trigger the small "signal" wire to close the solenoid, that is a question for Cummins, using your engine serial number. Suspect it will be the Cummins computer that sends the signal. Before you start, check for a loose or disconnected wire.

Re: Pre Heat controls for 8.3

Reply #8 – October 20, 2012, 06:11:07 pm

I would guess the engine is a ISC, If you could provide the Cummins Engine Number from the ID plate, I most likely can give you a clue.
Dave M

Re: Pre Heat controls for 8.3

Reply #9 – October 20, 2012, 10:49:46 pm

Larry,

Do you have the 'mechanical' non-computerized C8.3, or the later computerized ISC8.3?

Our C8.3 uses an intake manifold thermostat to power the 12 volt heater system.
I also would like a diagram on how this "wait to start" pre-heat system works.
Looking at our engine, I also see something that looks like fuel maybe injected into intake manifold as part of pre-heat.

I think this pre-heat system is an option for our engine, so all C8.3 do not have electric pre-heat. Foretravel specified Cummins to build the engine with pre-heat.

If anyone has description or diagram on this intake manifold heater, your assistance is appreciated.

Re: Pre Heat controls for 8.3

Reply #10 – October 21, 2012, 09:43:39 am

My 99 had a grid heater in the intake and it had a block heater as well. I had a sticker that said do not use ether on it as well. My ISM comes with an ether bottle and switch though I do not use it.

Re: Pre Heat controls for 8.3

Reply #11 – October 21, 2012, 09:50:46 am

John,

You are correct. Ether (starting fluid) and a red hot intake manifold heater are an EXPLOSIVE combination. Caterpillar and Cummins modern engines have intake manifold heaters, so ether is a real no-no.

Re: Pre Heat controls for 8.3

Reply #12 – October 21, 2012, 10:26:39 am

Does it makes sense to disconnect and cap off the M11 ether hose from bottle to intake manifold?

Even without the switch being used to activate the ether, would leaking ether from a solenoid failure be a problem?

Re: Pre Heat controls for 8.3

Reply #13 – October 21, 2012, 10:33:20 am

I thought about the same thing. I looked at mine and it was empty so I left it that way and bought a spray can to carry if I needed it. I did need it one time. The engine lost a sensor and would not start so I used ether and it started and drove to cummins and they fixed the sensor.

Re: Pre Heat controls for 8.3

Reply #14 – October 21, 2012, 11:03:59 am

Barry,

I have same setup as you with 8.3 mechanical.

There are fuel lines going to preheat controlled by solenoid.

I could not find the intake manifold thermostat to trigger preheat heater and fuel solenoid for preheat.

Larry Bradley
1998 u270

Re: Pre Heat controls for 8.3

Reply #15 – October 21, 2012, 01:01:36 pm

Larry,

I just found some info. . .

Attached are Cummins diagrams on our intake manifold heater. There are other option diagrams if these don't exactly fit. Shows location of the temperature sensor. And it shows a pressure sensor, too, that I wonder about.

You are not alone on hard start. A Google search brings up a lot of hits:
2001 Freightliner Fl80 ISC 8.3l cummins. Vehicle has cold - JustAnswer 0-isc-8-3l-cummins-vehicle-cold.html
I got 2004 freightliner truck mt55 step van with cummins engins..park - -step-van-cummins.html

Re: Pre Heat controls for 8.3

Reply #16 – October 21, 2012, 01:12:01 pm

I had hard start issues with my ISM especially if it was cold out. I found that there were 29 upgrades to the ECM that needed to be done and 13 of them were to address hard start issues. Starts right up with no issues even in the single digits now.

Re: Pre Heat controls for 8.3

Reply #17 – October 21, 2012, 07:01:37 pm

Thanks for the documents from Cummins. I stuffed them into my "RV" folder.

We have the C8.3-325 (all mechanical). The "Wait to Start" lamp on the dashboard stays on much longer in cold temperatures. It seems that our intake preheat system works properly. The engine starts well down to about 32F.

When the ambient temperature is below freezing, the engine turns over slowly or not at all. If we expect subfreezing temperatures at start time, I use the block heater that is controlled by the switch at the foot of the bed. If temperatures are going to be below 20F, I turn on the block heater at bed time in the evening. The block heaters warms the oil enough that the engine starts quickly.

Re: Pre Heat controls for 8.3

Reply #18 – October 21, 2012, 08:04:47 pm

Larry if you have an ISC 8.3 (Electronic engine) the heater grids are controlled by the engine processor(ECM) if I'm not mistaken via the intake air temp sensor. As someone else has said Cummings may have some updates for the problem. The control wire from the grid heater solenoid goes to one of the pins at the engine computer. Mine will work if it gets real cold, but if it gets below 40 and I have shore power I just turn on the block heater, and the boost sw before I go to bed, fires right up in the morning.

Re: Pre Heat controls for 8.3

Reply #19 – October 24, 2012, 10:34:29 pm

Larry, The Temp Sensor is midway back and just below the end of the injector on the right side of the engine. Cummins Application Engineering Bulletin Number 53.03 dated January, 1998 gives the complete write up on the preheat system. I have the 17 page hard copy but unable to convert to computer file.

Re: Pre Heat controls for 8.3

Reply #20 – November 09, 2012, 11:24:31 am

Attached is Tom & Lynda Whipps complete 17 page Cummins Intake Air Heater document.

It tells ALL about the "Wait to Start" system on Cummins C8.3 engines.

Not only does the document explain how the system works, it also gives us information on how to start these engines to maximize the pre-heat feature.

Thank you Tom & Lynda . . .

The pdf file is in two parts.

Re: Pre Heat controls for 8.3

Reply #21 – November 09, 2012, 12:29:21 pm

Thanks Barry and others. This sort of info and shared research is why I still haunt this forum.

When not having shore power, and not wishing to wait for the generator to "block heat" the engine for a cold start, I have had success with two or three cycles of the "Wait to Start". But have worried if I was pooling fuel in the inlet or setting up some other dangerous condition....

Re: Pre Heat controls for 8.3

Reply #22 – November 09, 2012, 04:49:38 pm

Very small note: Referring to RIGHT side of engine, in the Foretravel, that is the Drivers side as the engine is reversed / backwards, Hot Start does not know a RV user is reading their truck engine notes.
Either way, the 120 Volt AC heater is on the Drivers side on the ISM block.
FWIW
Dave M

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