A feeling of Deja Vu - 6.2 starting problem...

Hello Forum!

This is my first post on the 6.2L forum, and I hope it isn't too boring or lengthy for others to read. I thought I had this problem solved, but apparently not - it has come back to haunt me some more...

My 6.2 is in a 27' Pace Arrow Class A motor home (1984) on a Chev P30 dually chassis (1983) with a TH400, and a 4:10 rear end. I bought the rig 15 months ago, but it has been in storage until last month. I've only put on 300 or so miles, but have been upgrading the running gear and various appliances in prep for a trip to California on June 16th (we hope).

It has always started after a few revs, but the glow plug lamp stopped working after the second or third time I started the engine. Since then I press the "Emergency Start" button (links the house batteries with the start batteries for maximum amps), count to 10, then turn the key. I didn't understand the glow plug system until recently, and thought it might just be the bulb seeing as it always started.

I was installing a new stereo and had trouble removing the old unit, and must have disrupted something behind the dash facia without knowing it because the clock, cig lighter & horn ceased to work (blown fuse), and for the first time ever, it failed to start. Actually when I first noticed the clock had stopped and tried to start the engine, I turned the key and there was nothing. No turning over, nothing. An hour later I turned the key again and it cranked well but wouldn't start. That inconsistency worried me.

After doing some internet research and studying my Haynes Manual for the 5.7 6.2, & 6.5 diesels, I gathered up my tools and got ready to troubleshoot the problem. The key was still in the ignition, and without thinking I turned it to the "run" position and voila - the glow plug lamp was lit. So I turned it to the "start" position and she fired right up with no hesitation.

When she reached normal operating temperature I shut her down, and then finished the stereo install and buttoned the dash facia back up. Then tonight when I went to move the rig back to the storage area for the night, there was no glow plug lamp and nor would she start. Cranks fine, but won't fire.

Based on what I've read, it has to be something electrical in the glow plug system. I pulled the doghouse cover and air cleaner assembly to check the pink wire on top of the fuel injector pump, and with the key in the run position there was no voltage at the connector. I have examined what is visible from the top of the engine looking for the glow plug relay, the glow plug controller and what the Haynes Manual calls the amp gauge idle fuse, but I haven't found them as yet. The firewall in front of the engine makes it difficult to trace any wires to the various electrical parts and terminals that are mounted on the other side, so it became a guessing game.

Can anyone help me identify & locate those parts (glow plug relay, connector & idle fuse) so I can continue the troubleshooting process? Any other advice, suggestion or input would be greatly appreciated.

Thanks in advance for your help...

JT

Welcome

The fact that this is a Motor home chasis and of some age can add some issues. (Little different layout and possibly previous owners changes)

In a standard pickup,Burb or Blazer the 84 would have a roundish looking device on the LH rear of the engine near the back of the intake manifold.

This unit has a round plug with a small bundle of wires that plug into it, this is the controller.

The other component to this system is the glow plug relay which on a truck bolted to the LH inner fender.

Trace the glow plug wire harness from the plugs back and se where they lead.

The relay looks like a ford starter relay that you have found on the inner fender of most Ford pickups of the same vintage.


Now if your truck is a late 84 and into near 85 iot could have the one piece glow plug relay controller. This unit also bolts to the LH rear near the back of the intake manifold, it has a narrow flat plugin with probably 4-5 wires going into it.

The unit also has 2 larger lugs that allow the conection of the + power cable feeding the glow system and the wires that go to the glow plugs.

These two larger lugs have nuts on them and the cables usually have a little rubber boot that slips over the nut to protect it from shorts.

The intermitent no glow plug light can be due to a failing controler in either setup.

The no crank and the blown fuse ?????????? if the rig was ok until the stereo swap, I suspect that something got molested while the dog house was removed.

Possibly a wire or wires have become chaffed and are shorting intermitently.

These sort of things can be a problem on the older rigs, but once ferreted out, should not be of great issue.

Here are some pix of the two different styles of controllers.

This should allow you to adentify the parts you have.

The glow plug dash light is fed off the controller system and lights
only when there is power being fed to the plugs.

The early tall round units were a little more prone to troubles but either system can fail.

If you still have issues finding the parts, snap some good Hi res piccys of the engine with the dog house off an post them here.

We are happy to help.

Missy

no power at the pump, intermittent glow plugs,. maybe an ignition switch problem??

nick

Missy & Nick - Thanks for the replies! The year of my 6.2L was a little confusing in my first post as the CHASSIS was built in 1983 and the MOTOR HOME was built in 1984. So I usually refer to the engine being a 1983 model year not a 1984.

In any case, the images you provided were perfect and helped me identify both the controller I have and its location (tapped into driver's side rear of head with a 4 or 5 wire connector (?) on its top). I presume the connector just pops off the controller or is it a more complicated procedure?

The local GM dealership's parts dept. advised that the controller & the glow plug relay are no longer available through GM. I called NAPA, Canadian Tire & Lordco, a local parts jobber, and they quoted me $240.00 for a new controller and $39.00 for the relay - ouch! NAPA only listed the relay ($45.00) but no controller, & the Canadian Tire guy didn't know what I was talking about. The controller price seems a little expensive for what I see in the image - does that sound about right to you, or am I getting hosed?

I decided to order the controller from Lordco to make sure I have one ASAP, but I will try to find a cheaper source even if I have to wait an extra day or so to get it. Also, I have read in other posts that these controllers can be faulty right out of the box. I'll mention this when I pick it up, and suggest that if the rig still won't start with the new controller installed, I'll be returning it for replacement or refund. Is there any way of checking if the controller's good before installing it? (just in case the supplier's return/exchange policy doesn't extend to a $240 electrical component...)

It doesn't look difficult to install, but I am not a mechanic by any stretch of the imagination. However, I am well equipped with tools, always take my time, read & study all instructions, and know when I'm over my head. Are there any other tips, warnings or other suggestions I should be aware of before I get into it?

And thanks again for the help. I look forward to any input or commentary...

JT

$240 for an obsolete problematic component is crazy. The 1985+ controller was about $40 last I bought one (a few years ago, at Napa). VERY easy install/upgrade. More reliable, fewer parts, and less money.

The little plug on top of the controller has two spots that usually have some little bumps/bars or ??? you squeeze the little cap and pull the plug off the controller.


Ebay is the hot ticket for a new controller. I just bought a factory GM one still in the OEM box (NEW AND UNUSED) for $30

Maverick's recomendation is correct. simple rewire to use the later style contoller/relay

The early style unit was more problematic, but I have had them go 100K miles and 10 years and never a whimper.

The main reason that GM changed the design was to clean up the system and to cut the cost while doing so.

Having the two piece system costs more $$$$ to build.

Now on a pickup, Burb or Blazer if the contoller takes a poop, it is simple to use two quarters (Coins) or a small screwdriver to jumper the relay out on the fender (On a dark cold night) and get the glows hot and the engine running.

This can be done without crawling under the hood and getting filthy.

Been there done that. :)

BTW

GM has gone through in recent times and chopped tons of parts from the list of items that they stock.

There used to be a grand wealth of good stuff still available from Ma General, not anymore.

BUTTTTTTTTTT the aftermarket is fast picking up the slack on most all the stuff that US lovers of vintage GM Iron want to buy.


Good idea to carefully check over all the engine wiring harness and connectors.

Be sure that the fussible links at the starter solenoid heavy ++ terminal are in good shape.

This is where all the major power originates from on the older rigs.

The 82-84 6.2's used the two piece glow controller setup. 85 and later used the single piece contoller/relay.

Good luck


Missy

Robyn & DMax:

Thanks for the info. I apologize for the long messages - I try to be brief, but end up providing more detail than is necessary.

I am tempted to upgrade to the '85 - '93 6.2L controller as suggested, but my Haynes Manual says I would have to install a "Temperature Inhibit Switch" circuit which is wired in series between the G/P controller and engine wiring harness, and I still have to find the glow plug relay. I'm not confident I could pull it off, and worry I'd screw something else up along the way.

There is one ford-style relay mounted on the driver's side firewall, but I believe it functions as a battery isolator separating the pair of start batteries from the pair of house batteries. There is also a single heavy cable that routes from the house batteries to this relay that I believe connects both banks of batteries when the "emergency start" button on the dash is pressed (giving maximum cranking amperage if start batteries have been depleted). This is the button I have been pressing to start the rig since the glow plug lamp stopped illuminating (actually it has illuminated maybe 2 or 3 times since I bought the rig - the last time was the other day after the ignition went dead and then revived itself).

The book says to replace the controller if the glow plug lamp only illuminates once and fails to cycle on and off after the engine starts. That is the behavior of my glow plug lamp when it illuminates. But couldn't it also be the relay - if I ever find it - or a fusible link? What about the "20 amp gage-fuse" somewhere in the ignition circuit? I haven't found it yet either - any clues or suggestions?

Access to the engine is tight from the top due to doghouse location, and impossible for me from the underside due to a physical disability (cancer took most of my throat & neck, and I have to be very careful when on my back or risk death by aspiration - very freaky to experience!).

I also have a time problem - rig is parked in a "Restricted Zone", and management is at the end of its leash. They have lost their sense of humour...

I will take a series of high resolution pics of the rig today and post them to the forum for reference purposes. Maybe that will help locate & identify these elusive components.

Thanks a lot for your patience and understanding with this situation. I truly appreciate the help!

JT

JT:

Check on the back of the engine just behind the controller. Had an occasion to look at the same vintage motorhome as yours a couple of weekends ago with the same problems. His had the relay bolted to one of the tranny bolts on the drivers side top. There is a two wire connector going to it and one is the power. To get it started, just energize the larger of the two wires and you should hear the relay click. Keep it on for about 10 seconds and then crank the engine. Should serve to get it out of the parking spot anyways.

If the relay isn't there, just follow the glowplug wires back to the relay. Should be fairly obvious. The relay is the last component before the plugs. You could just wire in a momentary switch into the the above mentioned larger wire and mount the switch on the dash. 10 seconds and your good to go.

Bill

Quote:

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Originally Posted by convert2diesel

Check on the back of the engine just behind the controller. Had an occasion to look at the same vintage motorhome as yours a couple of weekends ago with the same problems. His had the relay bolted to one of the tranny bolts on the drivers side top.
Bill

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Bill: I found the relay - looks like it's bolted to the tranny bolt as suggested, but it's too tight for me to get at it. I installed the new controller, but it still just cranked & wouldn't start. When I plug in the connector to the g/p controller, the g/p relay clicks (cycles ?) on & off three times. This is when the key is in the "off" position. I checked the pink wire @ fuel solenoid again, and now I have 12.7vdc there.

My Haynes Manual mentions an "Amp Gage Idle Fuse" somewhere in the ignition circuit. Any idea where this fuse could be found? If it's under/behind the dash, it could have been disturbed when I replaced the stereo (which is when this all started to go wrong...).

Thanks for your assistance with this...

JT

JT:

The fact that the relay cycled a few times when you connected the controller with the key off, would suggest that somethings amiss here. There should be no voltage going to the controller with the key off. Have no idea what the "amp gauge idle fuse" is. Never heard of it.

Try working the circuit backwards from the relay. There are two wires going to the relay through a flat two wire plug. Not the battery/GP connections (large battery type connections). One is large (most likely what activates the relay) and a smaller one (probably the GP light. Check your Haynes manual for the wiring to the relay.

You should be able to pull that plug and apply 12V to the terminal connected to the large wire (make sure the controller is unplugged as I have no idea what feedback would do to the controller). The relay should click and you should be getting 12V to the plugs. Hold it there for about 10 seconds and then try a start immediately. If no joy, then check to see if you have 12V at both terminals on the pump (fuel stop relay and the cold start advance relay). If all checks out then you either have a bad GP relay, a bad controller or a bunch of bad glowplugs.

Bill

Quote:

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Originally Posted by convert2diesel

JT:

The fact that the relay cycled a few times when you connected the controller with the key off, would suggest that somethings amiss here.
Bill

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Bill;

A friend of a friend was kind enough to take a look, and quickly he narrowed it down to a couple of culprits. The power to the fuel solenoid with the key in the "off" position was a clue; also, there are a couple of wires recently tapped into the glow plug controller that lead thru the firewall and then back into the driver's side under the dash area, but we weren't able to see where they terminated. In any case, he giggled one of them, and that caused the g/p relay to click, and the g/p lamp to illuminate. But only for a moment. After wiggling a few more wires, and now with the key in the "on" position, when I pressed the "emergency start" button, the g/p lamp stayed on and after 10 seconds, I turned the key to the "start" position & it fired right up. A couple of minutes later, when I turned the key to the "off" position, the engine kept running; we shut it down by disconnecting the pink wire on the fuel solenoid.

My new friend thinks that the battery isolation relay (the Ford-style relay/solenoid mounted on the firewall in the forward engine compartment) is the most likely problem based on the fact that current only flows to the g/plugs & the g/p lamp illuminates when the emergency start button is pressed, and current is flowing from the house batteries not the start batteries. The ignition switch works for the starter and all accessories, so that isn't the problem.

At least we got it started and I don't have to tow it to a mechanic. We did install a simple "kill" switch on the pink wire to the fuel solenoid as a sure way of shutting her down when the key does not work.

It seems the only time that the g/p relay gets any current is when the emergency start button is pressed with the key in the "on" position. I am wondering if the two wires spliced into the g/p controller are somehow connected to the emergency start button, and when pressed current goes directly from the house batteries to the controller which then energizes the g/p relay & fuel solenoid that enables the engine to start. Does that make any sense to you?

BTW, after it starts to run, the g/p lamp cycles on & off a few times like it is supposed to, for the first time since I bought the rig. And it starts right up - maybe 5-10 revs - and runs real smooth as always.

Any other thoughts or ideas? I think I will have both the isolator relay & the g/p relay replaced asap. I don't need either of them causing problems on our trip to California next week. Are there any other things I should replace while I am at it? Your input is greatly appreciated!

Thanks again -

JT

Finally - it looks like the root problem to my 6.2L non-starting condition was a faulty alternator that was installed 150-odd miles ago. The supplier, Canadian Tire, replaced the alternator under its 3 year warranty last Saturday, but the speculation is that when one (or more...) of the bridge rectifier's diode's blew, the alternator started sending 16 - 17 volts of AC current down the signal wire which in turn cooked the glow plug controller. The controller then failed to manage the various switches and heaters resulting in no current to the glow plugs, and with no glow plugs - it's a no start scenario.

Somehow it also affected power to the fuel solenoid on the injector pump, the battery isolator relay & circuitry, and the emergency start override which became the only way the engine would start in such a condition. The alternator's internal regulator was also shot which caused the overvoltage situation was delivered to the 2 banks of new batteries as well. In view of what could have happened, I might have gotten away easy with just the $352 bucks for the new controller and an extra $230 installation labour that wasn't covered by the alternator's warranty.

Once the replacement alternator was installed, 14.5 VDC was delivered to the charging system, 12.2 VDC was measured at Pin 1 of the controller's connector, and all components of the glow plug system returned to normal operation.

Anyone with a similar glow plug system set-up would be well advised to watch alternator output for any significant charging overvoltage (anything over 14.5 to 15 volts DC) as a possible clue or forewarning before the glow plug circuit is compromised.

It's amazing how far reaching a faulty alternator can be, and I found it a particularly expensive and difficult to troubleshoot exercise that might have been easily avoided had I been more familiar with the g/p system.

Sincere thanks to everyone who was kind enough to respond to this thread with their helpful information & advice.

Have a terrific summer!

JT