6.9 IDI Strange Hardstarting issues.

[Ciulster]

So I have been messing around with my 6.9 IDI for awhile now trying to get it nice and reliable for the winter but I've still been having some issues starting it up. First off the engine has roughly 260,000 miles on it. Brand new rebuilt injection pump, fuel filter, fuel return lines, and two 950CCA batteries. The truck cranks over super fast so I know it is not a battery/starter issue.

I've looked around but every post I could find pointed me to air in the lines. I have tested the Schrader valve and looked for leaks all throughout the system. I can 100% confirm there is no air in the lines (no bubbles or drain back at all) and it is getting more than enough fuel. During excessive cranking it pukes unburnt fuel in the form of white smoke out of the exhaust so I know it has plenty of fuel.

Glow plugs were replaced last year but are on a manual push button system. I've never cycled them for more than 10 seconds at a time and no less than 5 second rests in between. I usually aim for 10-15 second rests. I crank and depress the accelerator halfway. The truck does not like firing and will usually only kick on one or two cylinders. Subsequent glow cycles and starting attempts later it seems to gain more and more cylinders before finally running under its own power. I have a video showing how hard it is to start right here:

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This cold start was done when it was roughly 50 degrees out. Notice the white smoke billowing out of the tailpipe after the first crank attempt and it slowly gaining cylinders after I glow a second time. I do not want to drain these brand new batteries right away just to get this thing started every day! It seems to be getting worse every day that goes on.

The truck runs absolutely PERFECT once it is running. Lots of power and no smoke aside from the little puff of black occasionally. If I shut it off for more than 5 minutes the truck will not restart unless I floor the accelerator and give it a little bit of glow plugs, which is leaning towards the symptoms of a heat soaked injection pump which I know can't be right because the darn thing is brand spankin' new!

So my question is, is this likely burnt out glow plugs or weak injectors? Or possibly even incorrect timing? Injectors have never been replaced as far as I've owned the truck and have unknown amounts of miles on them. Without glow plugs if I spray a little ether or WD-40 down the intake the truck fires up right away, and therefore probably has good compression, but dies as soon as it runs out of starting fluid to burn. Is it possible that I have caused a few glow plugs to fail during the abuse with weak batteries they saw last year or is this more likely a worn injector problem?

 

[fyrfghter]

Reminds me of when I was getting air in the fuel at the fuel heater


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[Ciulster]

Uh I am not so sure that could be it. As far as I know this truck has absolutely no fuel heater on it at all. It is the very first year they sold the 6.9 IDI's so who knows... but when I look at the fuel filter housing there are no electrical connections on it what so ever, not to mention when I depress the Schrader valve after sitting overnight fuel gushes out! In fact I've never seen a fuel filter housing like the one I have on any other IDI aside from 83's. (excuse the misplaced hose clamp there, we were working on new return lines, back in its proper home now)

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It certainly does not look like an air intrusion problem to me. I wish it were that simple.

 

[fyrfghter]

Uh I am not so sure that could be it. As far as I know this truck has absolutely no fuel heater on it at all. It is the very first year they sold the 6.9 IDI's so who knows... but when I look at the fuel filter housing there are no electrical connections on it what so ever, not to mention when I depress the Schrader valve after sitting overnight fuel gushes out! In fact I've never seen a fuel filter housing like the one I have on any other IDI aside from 83's. (excuse the misplaced hose clamp there, we were working on new return lines, back in its proper home now)

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It certainly does not look like an air intrusion problem to me. I wish it were that simple.

Yea I know yours shouldn’t have a fuel heater, just saying it was acting how mine was when it had air intrusion issues. Now if I could only get my other starting issues fixed...


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[david85]

This might be a long winded reply, but I hope it helps.

So I have been messing around with my 6.9 IDI for awhile now trying to get it nice and reliable for the winter but I've still been having some issues starting it up. First off the engine has roughly 260,000 miles on it. Brand new rebuilt injection pump, fuel filter, fuel return lines, and two 950CCA batteries. The truck cranks over super fast so I know it is not a battery/starter issue.

Is this the original 1983 engine? Curious because according to some, those had slightly lower compression. If it was 1985 or newer, I would suggest trying the block heater. If the block heater allows it to start easier, then its likely glow plugs not working. If its older than 1985.5, I would avoid using the block heater since this is rumored to cause cracks in the older blocks.

I've looked around but every post I could find pointed me to air in the lines. I have tested the Schrader valve and looked for leaks all throughout the system. I can 100% confirm there is no air in the lines (no bubbles or drain back at all) and it is getting more than enough fuel. During excessive cranking it pukes unburnt fuel in the form of white smoke out of the exhaust so I know it has plenty of fuel.

How long are you cranking before it starts showing white mist (raw fuel) at the tailpipe?

Glow plugs were replaced last year but are on a manual push button system. I've never cycled them for more than 10 seconds at a time and no less than 5 second rests in between. I usually aim for 10-15 second rests. I crank and depress the accelerator halfway. The truck does not like firing and will usually only kick on one or two cylinders. Subsequent glow cycles and starting attempts later it seems to gain more and more cylinders before finally running under its own power. I have a video showing how hard it is to start right here:

xc_hide_links_from_guests_guests_error_hide_media

This cold start was done when it was roughly 50 degrees out. Notice the white smoke billowing out of the tailpipe after the first crank attempt and it slowly gaining cylinders after I glow a second time. I do not want to drain these brand new batteries right away just to get this thing started every day! It seems to be getting worse every day that goes on.

White/grey smoke is expected as all the raw fuel cooks off. As for cylinders coming online one at a time, that can be caused by air or glow plugs not working, so we'll need more clues to narrow it down.

The truck runs absolutely PERFECT once it is running. Lots of power and no smoke aside from the little puff of black occasionally. If I shut it off for more than 5 minutes the truck will not restart unless I floor the accelerator and give it a little bit of glow plugs, which is leaning towards the symptoms of a heat soaked injection pump which I know can't be right because the darn thing is brand spankin' new!

Heat soak is usually a narrow window after shutdown...say, 5-20 mins. After that, a lukewarm start should happen without issues. Is that what's happening, or is it anything past 5 min? If its anything past 5 min and the engine is right up to temperature...well, I hate to break it to you, but you are still getting air in there somehow.

So my question is, is this likely burnt out glow plugs or weak injectors? Or possibly even incorrect timing? Injectors have never been replaced as far as I've owned the truck and have unknown amounts of miles on them. Without glow plugs if I spray a little ether or WD-40 down the intake the truck fires up right away, and therefore probably has good compression, but dies as soon as it runs out of starting fluid to burn. Is it possible that I have caused a few glow plugs to fail during the abuse with weak batteries they saw last year or is this more likely a worn injector problem?

Glow plugs are killed by running them for too long causing them to burn out. I don't see how weak batteries could cause that since there would be less power available to burn anything out.

Usually when a starting aid is used at temperatures as warm as 50F, the engine should fire off on the fuel and keep on going (unless this was early morning after a much colder night). Having to keep it alive with a starting aid is usually something that only happens below freezing, or fuel starvation (or both).

If you insist on using either fluid, please make sure the glow plugs are not powered or you could get a nasty backfire up through the intake. I'm also not a fan of using it at all, since its possible to cause a cracked upper compression ring. Having said that, many are able to get away with it by using very small doses.

Improper timing usually results in very poor running even after reaching operating temperature, so I think that's out.

Possible Causes:

If your problems were limited to only hard COLD starting, I would be tempted to blame the glow plugs. However, since you are also seeing poor restarts 5 minutes after a hot shutdown, the culprit is likely still going to be air in the fuel system. The fact that you recently disturbed most of the low pressure lines also leads me to believe something might be happening there.

If you look at the return line at the top of the injector pump, there is actually a check valve in there (between the brass elbow and the aluminum cover). It might be worth removing the elbow and pulling the check valve to inspect it.

EDIT: Here's the return line check valve location:

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Also, make sure there is a return line from the fuel filter head connected to the passenger side bank of injectors. Sometimes guys will remove and block off this line in an effort to chase gremlins. Its actually there to help eliminate air from the filter head before it can get sucked into the Injection Pump inlet.

A bad rebuilt Injection Pump MIGHT also be the problem, but if this was a quality rebuild, its not likely.

Fuel injectors have to get pretty bad before they prevent the truck from starting at all. HOWEVER, a leaking injector nozzle might allow air into the system. It would have to be a massive leak to show up as early as 5 min after shutdown though. If any dirt got in when the system was apart, this could be a problem.

 

[snicklas]

Couple other quick questions.....

1. How did you change the pump? Did you remove the pump from the gear tower, or did you remove pump, gear and tower all together?

2. Has it been timed? Timing can effect starting as well as other performance issues.....

Where did the pump come from, just because it’s a fresh rebuild doesn’t mean there can’t be a problem with it.

 

[bbjordan]

Since it fires up right away with ether, I think it is glow plug related. It could be burnt glow plugs. If the glow plugs test good, it could be the connections to the plugs. Also, just because the glow plugs test good, and the connections are good, and the GP relay clicks, doesn't mean the GP relay is good! Does the voltage drop to 8-9 Volts when you glow the plugs?

Because it dies shortly after, is the High Idle solenoid working? What RPM does it idle at cold?

Is the Cold Advance Solenoid working?

What timing are you currently running? Retarded timing can cause hard starts when cold, hence the CAS.

 

[david85]

Since it fires up right away with ether, I think it is glow plug related. It could be burnt glow plugs. If the glow plugs test good, it could be the connections to the plugs. Also, just because the glow plugs test good, and the connections are good, and the GP relay clicks, doesn't mean the GP relay is good! Does the voltage drop to 8-9 Volts when you glow the plugs?

Although I said air leaks, you're absolutely right that it could still be glow plugs.

The main engine connector near the oil dipstick is notorious for corroding. There should be two heavy gauge wires (orange with white stripe I think) going through that connector. I had to bypass mine years ago due to corrosion even melting in the connector. And yes, the other connections in the system could easily rob power from the glow plugs.

 

[Macrobb]

Honestly, if you are going with a manual glow plug setup anyway... Replace the glow plug harness.

Either 10ga wires to each glow plug, or, say, a single 4ga wire making a "loop", with 10ga "tails" soldered on that go to each plug.

Also, yeah, replace the relay - I found out that a "working" but old glow plug relay was dropping 2V across the terminals when it was on.
A new one was less than 0.5V under the same load...

 

[baja-Dean]

my 86 i found the similar symptoms. for the last year I put in a secondary electric fuel pump , i would turn on the electric fuel pump as I had it wired to the park side of the keyswitch. I turned it on for 5-15 minutes before I would turn the truck on depending on how long i had not used the truck from 1 day to 2 months. Always started AGAIN ONCE WARM.

last week i finally had fuel leaking under the truck, it was the rubber hose that is about 6 inches long feeding into the fuel pump. I replaced with properly rated fuel hose and I do not have to prime the truck anymore. Gee a rubber hose only 30 years old needed replacing, go figure.

 

[flexneck]

The truck runs absolutely PERFECT once it is running. Lots of power and no smoke aside from the little puff of black occasionally. If I shut it off for more than 5 minutes the truck will not restart unless I floor the accelerator and give it a little bit of glow plugs, which is leaning towards the symptoms of a heat soaked injection pump which I know can't be right because the darn thing is brand spankin' new!

as far as i know, one is supposed to run the glow-plugs every time before starting. my current one still has a fully intact original automatic GP shutoff, and it always comes on - it still has the sticker loudly stating to ALWAYS WAIT FOR GP LIGHT TO GO OFF BEFORE STARTING uglyfing the dash. my first was a push-button setup, so no voltage controlled shutoff, but it would not like starting without them, no matter how warm it was. just my 2c - also, the 6.9 needs continuos duty plugs, as i have experienced and documented in some other post. it will eat the other type...

 

[Ciulster]

So just an update here. I swapped in some old autolites I had lying around as an emergency GP system and the hotstarting issues have weirdly vanished. Cold starts are a little better. Currently warrantying my Motorcrafts and should have them back in by the end of the week.

The truck has outright refused to start the past few days and the batteries are getting pretty low. I checked the schrader valve and nothing. Just a hiss of air. I opened the valve while the truck was running and it took a full 15 seconds for fuel to squirt out. Truck lost a lot of prime real fast all of a sudden. I replaced the return line from the filter head to the passenger bank with a clear line and let it sit overnight. When I came back the next morning there was about an inch of air in the top part of the line. So not a huge ammount getting in but still none the less some. Fuel isn't frothy and has good pressure out of the schrader valve and through the clear line so everything before the filter housing seems in good shape. My air problem is either in the return system, injection pump intake system, or a bad check valve somewhere.

Upon checking the return line caps I found they are TOTALLY loose. It has been getting down to around -5 F up here at night so my theory is that the o-rings have shrunken up and gotten brittle to the point where they are leaking. I got some #111 o-rings and plan to replace them and maybe eventually get some Viton o-rings in there to help deal with the cold as it's only going to get colder from here on out.

My theory is that air must have been getting in overnight in the cold after contracting rapidly from full engine heat. When the engine is running the return system probably seals up better thanks to the heat and moving fuel help to expand and soften the o-rings. In the past few starting attempts I've probably sucked more and more air into the IP until it eventually got an airlock in enough injection lines where the batteries refused to crank it enough to overcome the airlock and start it today. I am going to install the o-rings and bleed the system to the best of my ability tommorrow and get back to you guys. Hopefully this is just a simple problem. I don't really feel like changing hardlines and fittings in a freezing snow flurry.

 

[bbjordan]

I can 100% confirm there is no air in the lines (no bubbles or drain back at all) and it is getting more than enough fuel.

It certainly does not look like an air intrusion problem to me. I wish it were that simple.

** cough **

Don't forget to change the "Olives" too. There is one on the fuel inlet side of the filter housing. One on the outlet side of the fuel filter housing. One on the fuel inlet on the IP. One on the top of the IP. And one on the back of the driver's side fuel return rail where it connects to the hard line going back to the tank.

I can't remember the sizes of them right now.

edit:

Courtesy of icanfixall:

"Our fuel system uses two different olive sizes. The 3/8 line fitting from the lift pump to the fuel filter is where that one fits. Then the 5/16 olives are for the line from the fuel filter to the injection pump. Then way back at number 8 cylinder intake runner is a brass fitting where you will find the last 5/16 olive. Its really hidden way back there but you will find it... If you have a turbo factory engine that fitting wont be there. Some older 6.9 engines had an olive on top of the return line at the injection pump too..."

 

[Ciulster]

I can't say for the rest of my fuel system but the old IP had the "olive" disintegrate..... either that or it was taken out at some point as it was completely non-existant when I changed the pump. I hope large ammounts of teflon tape is interchangeable with these "olives" as that seems to be what is holding together at least a few of my fittings right now.....

 

[Thewespaul]

I can't say for the rest of my fuel system but the old IP had the "olive" disintegrate..... either that or it was taken out at some point as it was completely non-existant when I changed the pump. I hope large ammounts of teflon tape is interchangeable with these "olives" as that seems to be what is holding together at least a few of my fittings right now.....

I believe you found your issue right there sir