Air intrusion on 1990 7.3L f350 with banks turbo

danda

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Ok guys, so I've got the classic hard start due to air intrusion. I bought this truck used in 2000 with 113k miles on it and have use it very infrequently, so mostly it has sat.

A few years back it developed the hard start symptoms and I replaced the glow plugs and return lines, which did not resolve the problem. It will start immediately if warm, but if it sits a few hours it will sputter a bit, and if it sits overnight it takes 10+ seconds of cranking, with strong batteries and a good starter.

This week, I've been trying to fix the issue, without success. Here's what I've done so far:

1. installed clear hose for the line between fuel pump housing and right front injector cap. (air bubbles would disappear after running for a short time.) btw, there is NOT a check-valve thingy in this one.
2. installed an electric fuel pump and removed mechanical pump (used block-off plate).
3. replaced o-rings and cap on rear injector passenger side because it was leaking a small amount. not leaking any longer.
4. ran hose from fuel pump to fuel filter housing, eliminating one "olive".
5. installed plug in the fuel filter housing outlet that goes to right front injector cap. (deleted) This was mainly a test to see if return lines are putting air in.

I have also ordered (not yet arrived) 2 olives for the hard line between filter housing and injection pump. This line is NOT leaking any fuel.

Ok, so after all this, I see basically zero improvement.

My observations:

1. On a cold start after sitting overnight, the engine does not come to life immediately then stall. It just cranks. This tells me that the injection lines have lost their prime somehow. The question is how???

2. Once started the engine generally runs well. It sometimes does some minor hunting during warm up, but it goes away before long. Engine purrs, has good power, clear exhaust at idle.


Questions:

1. Could this be a return line issue? Even if there is somehow error in the return line, I would think it should not cause the injector primary lines to lose prime. Unless maybe an injector is stuck open. But wouldn't that be noticeable when it is running?

2. Could it be a fuel supply issue? if there is air in the lines coming from the tank, well it doesn't seem like that should cause the injectors to lose prime either.

3. I do not see any visible fuel leaks anywhere. Is it common/possible that atmospheric pressure air is getting IN someplace although pressured fuel cannot get out?

4. Could this be an injection pump issue? I hope not....

5. What should I try next? I have the 2 olives on order. I'm considering replacing the fuel heater o-ring, or deleting the fuel heater. I haven't yet tried sucking fuel from a jerry can to eliminate possible supply issues.

I should also note that before this week the truck was sitting for years in a field. When I first tried to start it after installing electric pump I was still getting no fuel to injectors (verified by cracking them open). So I took the top cover off the injection pump and wiggled the spring mechanism back and forth and that seemed to unstick it and after that injectors were getting fuel and it would start/run.

Well I hope y'all have some suggestions. I've been reading through all the old threads I could find, but am still scratching my head.
 

danda

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thx for reply. Glow plugs were all changed a few years back and have approx 80 miles on them. That said, I suspect at least one is bad because I get some extra clicking from relay after the "Wait to start" light turns off. Yesterday I found one with the wire disconnected and reconnected it, but I still get some extra relay click, click. I did resistance test on 4 of them I could reach and they were all about 0.1. Today I will remove banks air filter and try and test the others.

There is a bit of white smoke on startup and acceleration. Perhaps this means one or more injectors is sticking open a bit? Would a single injector sticking open cause all the injectors to lose prime in a matter of hours?
 

gnathv

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The glow plug relay clicking is normal. The relay continues to cycle for a little while after truck starts. Does your block heater work? If it does plug it in for an hour and see if starting improves.
 

danda

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not sure if the heater works. I will try it and see. Anyway it has been warm days here, and my other diesel truck fires up no problem.
 

TNBrett

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I was asking about white smoke while cranking because that would indicate fuel being sprayed, but not igniting. That would be the case if your glow plugs were not working properly, and there wasn't enough heat in the cylinders to fire. The reason I ask is because it doesn't sound like fuel drain back to me. Normally it takes more than 10 seconds of cranking to clear the air out.

When you turn the key to run, how long does the WTS light stay on? Does it pull the voltmeter down? If you leave the key in run and don't crank it, it will start cycling the glow plugs on and off quickly for a little bit. Do you see the voltmeter bouncing during this?
 

danda

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yeah, your theory kinda clicked with me overnight. I wasn't really thinking along those lines before because I (perhaps wrongly) believed glow plugs to be working.

Ok so this morning I went to plugin block heater and discovered that the wire was (a) super brittle in places and (b) severed. I had to make breakfast, so for the time being I just stuck a 1500 watt ceramic heater under the pan (a little scary, probably won't ever do it again) and closed the hood. Left it a couple hours. Came back out and the block didn't seem noticeably warmer, but at least the pan was warm. Started cranking it. It started in about 5 secs this time and didn't stall, so seems an improvement. I should note that today is also a hotter day than yesterday... ambient temp was probably about 85F by then.

I forgot to check for white smoke during cranking. I'll go out with my wife in the evening and watch while she cranks it over.

For comparison, I cranked my '98 chevy 3500 6.5L without waiting for glow plugs at all. It started in 3-4 seconds.

I then fixed the ford block heater wire (cut and added ac plug) and plugged it in. I wasn't sure if it was doing anything, so I plugged it into a kill-a-watt meter to check, and.... 0 watts. So I guess that means the heating element is bad. I don't think I'll fix it, as this is california and I never needed it in the past.

To your q's:

I haven't timed it, but I would say the WTS light stays on 10-15 secs when it totally cold, and 1-3 secs when it is warm.

The voltmeter is a bit interesting. When I first turn the key on, it goes to 10v and kind of quivers there, basically steady. When the WTS turns off and relay starts clicking, the needle moves to 11v and then bounces between 10 and 11v with each relay click. Once the relay stops, it steadies at 11v.

I was curious about the low voltage readings, so I put a voltmeter directly on the battery at rest, and it was 12.45. Turning the key on dropped it to 11 something. I have also noticed that when the vehicle is running, the dash voltmeter seems low. I don't recall that being the case when I was actively using the truck years ago. So I'm wondering if this is perhaps indicating a bad ground somewhere, and if so, if that might be adversely affecting the glow plugs...
 

IDIBRONCO

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I haven't timed it, but I would say the WTS light stays on 10-15 secs when it totally cold, and 1-3 secs when it is warm.
That sounds pretty normal to me.
The voltmeter is a bit interesting. When I first turn the key on, it goes to 10v and kind of quivers there, basically steady. When the WTS turns off and relay starts clicking, the needle moves to 11v and then bounces between 10 and 11v with each relay click. Once the relay stops, it steadies at 11v.
This is perfectly normal behavior for the volt meter. While the glow plugs are heating, there's so much draw that the battery voltage drops a decent amount. That's why our trucks have two batteries. When the glow plug controller quits sending power to the glow plugs, the battery voltage will rebound back to it's normal reading. After the "wait to start" light goes out and the clicking starts, that's the controller turning off and back on again. That causes more draw so the battery voltage will drop and then raise again. If you watch closely, the battery voltage should stay low for a few seconds after the "wait to start" light goes off. This is because the controller is still fully cycling and it's before the clicking starts. Watching the voltmeter is actually a much more accurate way to tell when you can start the engine than the "wait to start" light is. It is possible that your glow plugs aren't quite heating up enough when the light goes off so it takes some extra starter cranking to get the engine to start. Since it's hotter outside, that could also reduce the starter crank time. You can test the theory out by waiting until the voltmeter goes back up or even until the controller stops cycling (clicking) to try to start the engine.
It's also not a good idea to try to compare how fast your engine starts to how fast your 6.5 starts. The 6.2/6.5 engine do start easier and faster than the 6.9/7.3 engines do.
 

TNBrett

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It sounds like the glow plug controller is working about like it should be. It’s probably worth it to check the rest of the glow plugs for continuity. Also the lower voltage readings at the dash vs at the battery could simply be from poor connections on that circuit, but poor connections on the battery cable could be at fault as well.

How is the cranking speed? If it’s not cranking very fast, it will take significantly longer to start. If the cranking speed matches the tempo of “row row row your boat” that’s not good enough.
 

danda

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cranking speed is fast and I've been keeping the batts charged. no issue there.

I was curious about total amperage being drawn when the plugs are active because I saw elsewhere on the forum that it should be in the range of 200-230 amps, so about 25-28 amps per plug.

I stuck my clamp meter on the negative cable for one battery and turned ignition on. reading was 107 amps. Then I repeated for the other battery and the reading was 70 amps. For total of 177 (including approx 2 amp for the elec fuel pump). I'm not certain if that's a valid way to test or not??? But if we pretend it is, then at ~175 amps, it means that 1, perhaps even 2 plugs are not heating.

I was having erratic reading trying to do resistance test and my test light bulb appears burned out, so I pulled a couple of the easiest to access plugs and inspected. They are beru, look fine, and when I hooked to batt with jumper cables, both glowed red along full length in 4-5 secs.

maybe the next step tmw is to obtain a functioning test light and test them all that way. I'd rather not pull them all, esp since a couple are kinda hard to access behind the banks turbo.
 

danda

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oh, also I checked that voltage between battery positive and glow plugs body (and other points on the motor) is the same as battery voltage between posts, indicating the ground is good.
 

danda

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Ok, I believe I've eliminated the "bad glow plugs" theory.

I made a little test light using an old tail-light bulb of unknown resistance with leads soldered to it. I then checked it against 2 known good beru plugs and 2 old questionable autolite plugs, one with an expanded tip. The expanded tip plug did not light the test light, while the other three did. So that tells me the test light is at least a somewhat valid way to test. (I also tried the jumper cable method, and all four lit up cherry red.)

So then I tested all 8 in the cold engine (sat about 24 hours) with the test light, and all lit up. Seems all is well unless there is some problem with the wiring or controller.

Next, I had my wife take a video while I cranked. Cranking lasted 9 seconds before it started. There was no smoke to speak of until the last few seconds, which I think is a strong indicator that injection lines lost their prime somehow.

Which brings me back to the question: how? Could this be caused by a faulty injector?

Anyway, here is the video, please let me know what you think.

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edit: btw ambient temp is about 90F.
 

IDIBRONCO

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Could this be caused by a faulty injector?
I would doubt it. The most that I can see that doing would be to drain the fuel out of it's individual fuel line. Have you tries pushing the Schrader valve by the fuel filter after sitting for 24 hours, but before using the starter or electric pump? There should still be fuel pressure there if your fuel system is intact (no leaks).
 

danda

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I will try pushing the schrader tmw am.

I can say that when I had the clear tube hooked up between #1 injector and fuel pump housing, the top of the tube would get air bubbles after it sits. But I'm unsure where they come from.

As I understand it, if there is air in the low pressure line *only*, the engine should still start initially, then stall quickly as the air gets into the high pressure lines. I don't get that initial start though...
 

Big Bart

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I haven't timed it, but I would say the WTS light stays on 10-15 secs when it totally cold, and 1-3 secs when it is warm.

If you are saying when the truck is at room temp and it’s 65 degrees out the glow plugs only run for 1-3 seconds, I’d sany that is too short in my opinion. If you are saying when the truck has been driven and is hot, you shut it off to get say diesel, then upon starting they go out in 3-8 seconds that is normal.

When the 7.3 style controller is not working because of bad gp‘s or a wiring issue the WTS light goes on for 1-2 seconds, senses a problem, then the WTS light shuts off and cycles the controller relay. So if tomorrow AM you go out to start the truck cold and the glow plug light only stays on 1-2 seconds, you have a problem. It is not warming up your glow plugs to hot so it can start.

You can test by seeing if the big post on the controller relay without the metal tab has 12v. If yes turn the truck ignition to run, then by touching a ground wire to the white wire on the small post on top of the controller relay, it will click, start powering the gp‘s, so count to ten (Glow plugs will now be hot.), and quickly try starting the truck. If it starts faster you need to check or replace the gp wiring harnesses (Classic Diesel Designs.) or perhaps replace the controller.

Other places you could have air intrusion. 1) On the bottom of the fuel filter, the water sensor o-ring. 2) On the top of the fuel filter housing is the heater element, its o-rings may be leaking as well. 3) One of the return lines or caps you did not replace.

Add some pics and let us know what you find out.
 
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