1986 F350 IH6.9 electrical challenge.

[flexneck]

hi there

i'm a noob to this site, and have spent my last few evenings after work and messing with my truck here to trying to figure out whats wrong with my old *******. after learning a lot more than i ever wanted to know about the basics of the IH 6.9, i finally have it down to the following situation:

at first, the truck would not start as soon as it dropped below freezing at night. i went to the obvious, check the glowplugs - note: they are bypassed, as in i have a toggle on the dash that directly energizes the relay. all the wires are messy, but i have continuity and at least power to all of them, i replaced one that was not working. so even if the wires are not the greatest, i figure i have a tleast 6 out of 8 working at the moment. initially, after doing all this and charging the batteries, it fired up right away.

then, 2 days and a few trips later, first the temp & oil gauges went all the way to the left (H), and stuck there. i stopped, tried to shut her off, and noticed that she slowly stalled, as opposed to immediatly shutting down - obviously the FSS was not actuated properly. opened the hood, checked all hoses, released pressure on the rad - everything nice and warm, but no steam or anything indicating that she REALLY was overheating or squeezing oil out the top. got back in, fired her up - no sweat, but still funky gauges, and reeally slow and wimpy turnsignal indicators on the the dash (dunno how /if the signals were working, was driving with no companion)

then, stop at the jobsite, shut her down (same slow stall instead of immediate shut-off), do my thing, come back about 45mins later and turn the key. nothing. like, zilch, nada, nix, DUH. all i see is the glowplug light come on. BUT remember, my g'plugs are bypassed, and i didnt turn them on, cuz she still would have been warm - normally, shes good to start in cool weather for about 2 hours at least with a warm block without using the g'plugs.

so now im REALLY worried. i try the hazards & headlights - nothing on the headlights, nothing on the exterior lights on the hazards either, BUT the bloody glowplug light starts flashing with relay clicking - all this with the key in the off position. with it in on, the hazards do nothing at all, not even flash the damn glowplug light.

so now im not only worried, but depressed - i messed with wires, wiggled cables and took apart half the dash without avail. called the AAA guys, buddy comes, laughs at my rats nest of wiring under the hood, tells me he's not gonna touch it (cant blame him) and just jumps the old girl straight from the starter solenoid. BLAM,cough, belch, and shes running like a champ. i run to the dash, and check it out, everything is kinda on, pulsing with the alternator at idle, but nonetheless, its kinda there - the gauges are still pegged at (H), but shes running. so i peel out, drive straight home and shut her off - shuts down "OK", just a little lag, and on trying, starts again within a minute or so.
then i go home, after losing a half-day of work, and spend my evening here, on Oilburners.

so today, the morning after all this, i go to apply my new knowledge about the ominous ignition-switch issue on these trucks, and check whats going on with my key/switch position. turns out, if carefully place it on "ON", everything looks good (gas-gauge comes on, lights nice and solid etc.) - if its a little off, it gets weird. so there is something up with it, but it does actuate the starter, and returns to its proper position mostly when released. starter cranks strong to, g'plugs seem to do it, at least the blower motor gets noticeably slower when i turn 'em on - BUT she wont fire now, just a little cough here and there. the FSS rod is a little sticky, but not serious, and helping it out all the way is not making a difference.

i'm starting to lose my cool now (never mind work), and really would appreciate some good ole' advice on what the F is going here - thanks in advance for your much appreciated input!

flex

 

[BigRigTech]

Almost sounds like you have a bad ground somewhere or a corroded wire....The large yellow wire that runs from your starter solenoid to your ignition switch might be "green" somewhere and allowing 12-volts to go through but very little amperage due to the incresed resistance. Most likely at the engine block to frame or battery to frame. Clean all your starting and charging connections and start looking to see if you have any voltage drops in the main supply circuit to the ignition switch......Hard to trouble shoot electrical issues over the net....

 

[suv7734]

I second the ground and battery connections. I had one here a while ago showing all kinds of erratic/goofy symptoms some similar to yours. We took the connections all apart (I usually start there so I'm not troubleshooting for nothing) cleaned everything really well and made sure everything was snug. Fired right up first shot and apparently been like that since. If that doesn't work PM me I'm not that far away.

 

[MIDNIGHT RIDER]

My truck has not done it in years, BUT, a number of times in the past, I would catch all my gauges going all the way over to right, ******* the needles.

The first time I about panicked, as I had on a big load of cattle, right in the middle of town, after dark.

I found that I could tap the clear plastic face over the instrument panel and the gauges would return to normal.

Someone on here stated what was causing this; but, it hasn't been a problem in a long time.



ALSO, both times that my alternator went bad, my gauges and the rest of the system behaved in much the same manor as you are describing.


I would suspect the alternator.

 

[RLDSL]

I've had the same thing happen on other vehicles with loose wires at the alternator, bum alternator/voltage regulator, and loose slipping belt on the alternator.Along with the dirty or loose ground connections. Check the cable ends to see if you get good contact when you flex the cables at the ends.

---------Robert

 

[Agnem]

There are schematics available to you if you check the links in my sig. You may be having multiple problems....

Gauges pegged - could be a bad IVR.

Slow shut off - Not electrical related. Are you using a fuel additive?

Definite power problems. You should not see pulsing lights. Use the schematics, and check all your wiring and grounds. Get rid of the rats nest! Clean it up, and return it to stock so we all can talk about the same wires.

Pull the pink or purple wire off your glow plug fender relay, and use a piece of wire instead to control your glow plugs and starter relay until you figure out what you've got going on.

 

[flexneck]

Just a little update - i sorted out the ratsnest, tore the dash apart, traced power and finally replaced the wimpy little ground wires leading to the battery terminal. that did the trick, as you guys correctly had assumed, and i did also repair all the BS that had been done by all the half-cut previous owners on lazy weekends. i even replaced 7 out of 8 glowplugs, the last one i cant get out without un-bolting the fuel lines, it seems. sounds great, huh?

the ******* still wont start, i even replaced the starter now because i killed the old one while bleeding the fuel line after starting it without fuel coming from the rear tank (which doesnt send, but thats a different matter).

it seems that i have air entering the system (but please correct me...) - so my first question is:

if i press the check valve on the filter before the injector pump, without cranking the engine, should there be fuel coming out?

i would like to add that i did get it to run after bleeding it forever, with back-off injector-nuts, and pouring a healthy mix of quickstart and diesel down the intake. after belching the expected toxic cloud, it happily idled for 25minutes and then drove fine down the block and generally made a healthy impression. however, this was 2 days ago, and now it wont even cough.

the second question is just for some advice on how to intelligently troubleshoot my fuel system without wasting tons of time, as i already feel maxed out in that department.

thanks again for all your advice so far, it proved very valuable indeed. without it i would have not even known where to start.

flex

 

[Agnem]

my first question is:

if i press the check valve on the filter before the injector pump, without cranking the engine, should there be fuel coming out?

i would like to add that i did get it to run after bleeding it forever, with back-off injector-nuts, and pouring a healthy mix of quickstart and diesel down the intake. after belching the expected toxic cloud, it happily idled for 25minutes and then drove fine down the block and generally made a healthy impression. however, this was 2 days ago, and now it wont even cough.

flex

Ack man! You sure know how to send us running for the hills!

NEVER pour liquids in your intake! They get really REALLY hard to start with bent connecting rods and low compression.

Here is what you need to do.
1) - Install an electric fuel pump if you haven't already
2) - disconnect the fuel RETURN from the injection pump AND the glow plugs.
3) - energize the electrical system and see if the fuel pump runs
4) - Watch for fuel coming out of the top of the pump
5) - if you have fuel there, reconnect the line. Put a clear plastic or vinyl tube in place of the fuel return line from the filter head to the passenger side bank. Use that to watch for air.
6) - Apply full throttle to the injection pump
7) - Crank for 6 seconds.
8) - Loosen and retighten each injector line at the injector, and listen for a little SSSFFFFITTT kind of sound. This is the air coming out.
9) - Go back to step 6 and repeat until you see smoke at the tailpipe
10) - Connect the glow plugs and start engine.

 

[flexneck]

Hi folks,

a million thanks for the concise fuel-system-bleed-manual. it worked great, i also capped the return line from the fuel-filter and that certainly made fuel flow instantaneous. maybe one day i will make an effort and find the air-leak...
but meanwhile it seems that my glow-plugs are getting eaten alive. at first i went through a fresh set of AC Delcos, that promptly swoll up, because of a wiring f*ck up of my own making.
after that, i just bought a set of fresh Bosch plugs (because i wasnt about to sacrifice a set more expensive ones, my wiring confidence being somewhat humbled). they seemed to die right after hitting my bypass switch. so i pull a few out, they are not swollen but quite dead. next, i plug an ancient un-identified gp into a random gp connector, hit the switch, and the thing works right away. i continued to try all my old gp's, but i ofcourse i didnt have a new one left - they were ALL toast, without the engine running once. i made two attempts to crank it, after killing the gp-relay ofcourse, so at best they got splashed a little with diesel, but no engine temperature ever touched these gp's.

what the hell is going on? how can it be that the old gp's work, some better than others (some of the tips are just crud, but even those get hot at the shaft) and brand-new ones seem to die as soon as they touch the engine?
am i missing something here, but even the worst gp would not die within seconds of powering it up? any gp should be able to handle 13v at the max, at least for a few seconds?

once again,
clueless flex

p.s. just for clarity: i got solid power on all plugs, continuity is good, wire resistance is minimal, and the connectors are clean and tight. the relay has a healthy *click* to it, and i just replaced the melted plug from relay to harness with some heavy duty connectors.

 

[Agnem]

Given your wiring issues, the first thing I would do is connect a test lamp to one of the feeds to a glow plug. You want positive indication that your glow plugs are receiving power at the right (or wrong) times. The 83 to 86 glow plug controllers are a known menace, and you should consider bypassing yours permenently. Relying on it to not kill your plugs is risky at best. As I said, take manual control of the pink wire on the fender relay and you will be safe. All your glow plugs need to be new Beru's. Do this test - install fresh plugs and put a volt meter on the plug (with the connector on it - a small piece of wire will facilitate the probe connection) at the #2 cylinder. Affirm that you have zero volts. Apply battery voltage to the stud that the pink wire was formerly connected to (you don't need to have they key on) on the fender relay. You should see 6 yo 7 volts on your volt meter, and over the course of 10 seconds that voltage should slowly rise to close to 11. Remove power from the stud after the 10 seconds, and observe that your voltage is zero. If you see more voltage than 6 or 7 at first contact, or your voltage rises less than 4 volts, you have open connections to some of the glow plugs. This can burn out the active plugs because the recommended 10-13 second burn time is based on a total system resistance that is comprimised as plugs fail. You end up with a higher voltage longer than you would otherwise. Also if you replace the wiring with heavier gauge wire so that the system can draw more current, you may increase the voltage available which could also shorten the needed burn time. There are a lot of variables here such as the health of your batteries, the condition of the fender relay and resistance increases due to connector or crimp corrosion or loss of grounds that can affect all of what I just said, but assuming everything is nominal these are the results you should expect.

 

[icanfixall]

You need to use the Motorcrft Beru glow plugs. The AC Delco, Autolite & Champion are so crappy they will burn out and swell up on you. Wellman is another good plug but they are expensive. How long are you holding the power on for the glow plugs? How long have you been running with the return line caps on the injectors. If they are painted grey they are leaking air into your fuel system...

 

[flexneck]

Thanks for the quick replies - currently i am too broke to buy more gp's, but i will make sure i save up for some Berus.

Agnem: my gp bypass is a hot wire from a switch on the dash to the relay - the pink wire was turning on the gp's as soon as the engine was running and that was what cooked my gp's the first time round. it is now removed. now i only have my brand-new wires, connectors and switch hooked to it.

i have measured the voltage many times in the last few weeks, with old and new plugs, and each connector has power. but i never noticed a gradual voltage increase - it just sits at about 11.5, about a volt lower than battery.
how would this gradual voltage increase come about - please excuse my obvious ignorance, but nothing is controlling voltage, its just 1 fat wire splitting in to 4 thinner ones on each side of the engine?

as i mentioned earlier, i only have 4 working plugs now, no more cash, a really pissed off wife, and a boat anchor truck. is there a way i could test out this gradual voltage increase with just 4 plugs, as in: i install the 4 gp's on the driver side cylinder row (basically one of the two main feeds) and watch for the voltage to rise about twice as fast as you were suggesting. like, instead of rise from 6v to 11v in 10 secs, 6v to 11v in 5 secs?

icanfixall: my lines are grey and leaking air into the system. i will deal with this problem once i sort out this gp problem, as the leak at this stage is not the show stopper. it will start perfectly fine when warm etc.

thanks again, without this forum & site i probably would have slit my wrists a few times already.-)
flex

 

[Agnem]

I have to confess, that voltage increase may be a function of the 7.3 controller, and may not exist on the 6.9's. I'll have to see for myself sometime. It comes about because the glow plugs offer a virtual dead short when they first come on, drawing the battery level down. As they heat, the resistance increases until it is such that they are using only a fraction of the power originally required. This is why many notice the dome light dimming when the glow plugs kick on, or the dash lights flickering or whatever. The 7.3 controller actually uses this voltage level as a management factor, ignoring time. This is why a dead plug or two on a 7.3 render the whole glow plug system useless.

 

[flexneck]

It Lives - for now...

so the truck seems to be healed. it took a set of Wellman dual coils, presto, truck starts, every day, not just once, after cooking the GP's. and heres why:

the controller on the 6.9 is a "fast glow" design from back in the day. this means it just hits the GP's with 12volts, for a relatively short period (quick resistance cut-off). this works fine with the original plugs (Beru/Motorcraft), but they are not made anymore. modern plugs are not designed for this crude system, as Agnem pointed out the 7.3 has a voltage regulated system, slowly increasing the voltage from 6 to 12v. this is standard, my 300SD Benz does this to.

so, if you are using a 6.9 with an oldeskool controller or pushbutton that activates the GP switch, you will need to buy so-called "continueous duty" or dual coil GP's, such as Wellman #6088. everything else will not last, probably not even stealership motorcrafts of recent manufacture.

the other option is to rig up the 6.9 with a 7.3 controller...


so, now on to the 21487275340967 other things that are falling off, rotten, rusted out or plain broken on the old *******...-)

thanks for all the help, without it i pro'lly would have thrown the truck off a cliff a month ago.

flex

 

[BigRigTech]

Good to hear you figured it out. It's not my nature to run from a challenge either, the harder it is the more stubborn I get....I haven't turned a wrench in 2 weeks at work, I've been doing nothing but electrical troubleshooting work....It's that time of year for wires sprouting green spots and snotty connections....One job after another, I had to replace an entire OEM Detroit engine harness last week because it looked like it had green chicken pox...