Adding clear fuel lines for air in fuel line tests.

[Vlad_p01]

RV idles (smoothly) for 3 minutes, or 1min, or 10 seconds several times (then cuts off suddenly) during a cold start before finally running well for as long as needed, after several tries. Can that be related to air in fuel lines? Before I add clear hoses to watch for bubbles. Few questions:

1. A clear fuel line at hose labeled (2) would show fuel going to hard line (3) and to the injectors? What the hose label (2) called?

2. The hose label (1), is that my return line?where does it go to. Replacing it would show me the fuel coming directly from where to the injection pump? Directly from the Fuel Filter Manager? Where can I follow it all the way to and replace it.

3. Will replacing the return lines between my injectors with clear ones to see any bubbles benefit me any in seeing if I have air in fuel?

4. Do my fuel lines need to be heat rated. If I’m not mistaken one of them will go under the intake manifold into something else, isn’t it hot there? Where to get heat rated clear fuel lines.

 

[ak diesel driver]

That screams PMD

 

[Vlad_p01]

That screams PMD

I thought the PMD would malfunction once it’s overheating. After a long time driving. Not necessarily?

 

[Will L.]

Nope. The heat does the damage but the actual failure can be anywhere, anytime.
Intermittent or constant. I agree with Ak dd. Probably the pmd.

That said…
Fuel line you labeled as 2 - that is the ip return line. Return is the only 1/4” line in the truck. That as the one to replace with clear line and leave it clear for ever. You will have to replace it about every 5 years or so. That is the one to watch for bubbles and contaminants. Don’t bother replacing other lines with clear because of the heat issues unless it is a diagnostic issue that you can’t get rid of bubbles.
Half a book into details on that, for now just replace the 2 line with clear.
You can get it at any hardware store. Best is to get some from https://fuel-line.com/
I suggest using screw style hose clamps on the clear hose.

No advantage to replacing the lines between or after injectors, causes more failures- don’t do it.

I can’t see line 1.
When you load pictures, please select FULL IMAGE not thumbnail. It helps people like me who only use mobile devises see the full picture.
Regardless, the only line to mess with right now is the 5” long 1/4” diameter return line you labeled as 2.

 

[Vlad_p01]

Nope. The heat does the damage but the actual failure can be anywhere, anytime.
Intermittent or constant. I agree with Ak dd. Probably the pmd.

That said…
Fuel line you labeled as 2 - that is the ip return line. Return is the only 1/4” line in the truck. That as the one to replace with clear line and leave it clear for ever. You will have to replace it about every 5 years or so. That is the one to watch for bubbles and contaminants. Don’t bother replacing other lines with clear because of the heat issues unless it is a diagnostic issue that you can’t get rid of bubbles.
Half a book into details on that, for now just replace the 2 line with clear.
You can get it at any hardware store. Best is to get some from https://fuel-line.com/
I suggest using screw style hose clamps on the clear hose.

No advantage to replacing the lines between or after injectors, causes more failures- don’t do it.

I can’t see line 1.
When you load pictures, please select FULL IMAGE not thumbnail. It helps people like me who only use mobile devises see the full picture.
Regardless, the only line to mess with right now is the 5” long 1/4” diameter return line you labeled as 2.

Thanks, that answers my question very well. I attached another photo, maybe that helps. Line 1 goes right under the manifold.

 

[Will L.]

Ok, line one is the supply line that goes from the ffm (fuel filter manager)
to the ip (injection pump). When stock, it is 5/16” diameter.
All the rubber fuel line (except the short clear piece described above) needs to be SAE30R9. The original line is not in pickups (idk what is in the rv) but back then there was no alcohol in the diesel fuel back then.

However when replacing that line, it is worth upgrading to 3/8 line and fittings- don’t do it now. Solve the current problem. Later when making improvements read up about “FTB -Feed The Beast”
modification. But better than alternating the factory filter is replacing the lift pump and ffm with a much improved unit like the FASS. Again- this is info to look into later. Do NOT make multiple changes at once. A simple error can combine with another problem and make diagnostics insanely difficult.

 

[snarl95]

How are the grounds? The motor only stalls when cold? Any codes?

 

[Vlad_p01]

How are the grounds? The motor only stalls when cold? Any codes?

I cleaned the grounds that I could find. It was only 3. I’m sure there’s many more, if I had a list or diagram I’d clean them all. Cuts off even when it’s not that cold. Like 45F. The mechanics couldn’t read my codes even with his 12K$ machine. He said I don’t have an ECM

 

[Will L.]

He is wrong- you do. He just doesn’t have the right one. You need a tech2- the gm scantool. There is a good chinese made fake one on ebay. Search the threads here to find details.
If you’re gonna own old metal- ya gotta know how to swing the hammer yourself.
There will be some money to invest getting the tooling needed, and doing mods to eliminate the engine weak spots. But once the painful part is done, these turn out to be great engines with low long term costs.

 

[snarl95]

I'm going with failing PMD. Does it stall while your driving it?

 

[Vlad_p01]

He is wrong- you do. He just doesn’t have the right one. You need a tech2- the gm scantool. There is a good chinese made fake one on ebay. Search the threads here to find details.
If you’re gonna own old metal- ya gotta know how to swing the hammer yourself.
There will be some money to invest getting the tooling needed, and doing mods to eliminate the engine weak spots. But once the painful part is done, these turn out to be great engines with low long term costs.

Oh Thanks! (What type of tooling?) I wander which one of these Amazon ones it is. Gonna do some reading and search around.

 

[Will L.]

Tech2

Almost none of the other scanners will work properly with it.
This ecu was the first one gm designed on obd 2

 

[jrsavoie]

tech2 scan tool - Google Search

 

[Vlad_p01]

Tech2

Almost none of the other scanners will work properly with it.
This ecu was the first one gm designed on obd 2

I’m finding varying prices between 260$ - 600$ I can find a good one. Thanks!! Couldn’t have guessed this.

 

[Vlad_p01]

Bullet point updates.

1. I put in a clear return line (last week)
as seen in the photo. Not the slightest air or bubbles when I did the test today.

2. Turned it on, engine idled fine. First for 15 minutes before it turned off. Then idled fine 30+ minutes til I finally turned it off myself. (usually it’s, 2 minutes, 10 seconds, 4 minutes).

Other info:
This test was preceded by 5 days of cold -19C weather. RV just sat there.

3.Didn’t rev it for a few days during that cold, battery was dead. Jumped it.

So today it idled fine. Is that related to the cold couple of days. Can the cold have frozen something (stuck) off.. changed something? Related to letting it sit 5 days. To the new return line? Was something wrong with my old line?

5. By the way that new fuel return line leaks as shown in the photos but it didn’t before, it must be because I installed it not tight enough.

I was trying to point out anything out of the ordinary. Is my air in fuel test done? Should I put a clear line somewhere else? Should I redo the test? Do something different before I rule out air in fuel? Thanks

In the photo is where the diesel drips. About one drop per 1 or 2 seconds.

The other photo is my old return line. Doesn’t look damaged to the eye.

 

[Glagulator]

Could be that IP OS filter, you don't need it.
Do you know if you have an OBD1 or OBD2 system?
Do you know where the PCM (computer) is?
Should be inside the cab.
Does it have PINK & BLUE or BROWN & BLUE connectors?

 

[MrMarty51]

Fourth pic from top. The clear line.
Hose clamp needs to be moved down onto the fitting then tightened up.

 

[MrMarty51]

The OS Filter that @Glagulator mentions is an electronical device that is quick connected I believe into the power feed line to the shut off solenoid. I think I have heard mention that it might be for radio noise suppression only.
I have also read that it can be disconnected at both ends and then removed and the terminal end thats left can be hooked direct to the fuel shut off solenoid.

 

[jrsavoie]

Not to the

The OS Filter that @Glagulator mentions is an electronical device that is quick connected I believe into the power feed line to the shut off solenoid. I think I have heard mention that it might be for radio noise suppression only.
I have also read that it can be disconnected at both ends and then removed and the terminal end thats left can be hooked direct to the fuel shut off solenoid.

Fuel shut down solenoid it goes to the Injection Pump.
All the fuel shutdown solenoids I remember having their own 2 wire connector.
Please correct me if I'm wrong.

A plugged return line can kill the engine. I've had return line issues 3 times.
An old collapsing return line can cause issues.

One of the early and easy tests I do, is to run the return line to a container, to verify flow and to see if it makes a difference.

 

[Will L.]

Fix that leak for sure.
As mentioned plugged return line will impede running, carefully cut open the old return line - just slice in half length wise to inspect.
You might have a restriction in the return line farther back that is being masked by the leak.

You could have a loose connection on fuel line supply that the now colder weather is masking. Happens with going to hotter days also. All you can do for that is keep an eye on that clear line you just added. A small trapped bubble collecting there is normal and fine. Traveling bubbles is the clue something is wrong- so just leave the clear permanently.
When problems occur wether tomorrow or ten years from now, inspect the clear line.
Bubbles traveling means there is a leak- usually from the tank to the lift pump. Since that section is under a vacuum draw of the lift pump, instead of dripping fuel out it will suck air in.

The fuel in a diesel gets built up to thousands of psi pressure for the system to work. Air will compress at a much easier rate than the diesel fuel so it makes the fuel injection system not operate properly. Sometimes it will run rough, sometimes sporadically, sometimes won’t let the engine run at all.