Under-performing 200tdi. Air in fuel lines.

[lcdck]

200tdi installed in a 1988 90. I did the install. Engine runs fine, puff of smoke on startup and occasionally if under load but no stumbles, smooth idle, etc.

I'm only able to do high 50's to maybe 60mph. I think I'm getting air in the fuel lines overnight and while running.
When I open the bleed screw at the top of the fuel filter housing I get tiny little air bubbles but it goes to straight diesel within seconds.
I replaced the spill return lines with new hose and this seemed to help but still not getting full power.
I tested the fuel lift pump by removing the hose to the diesel filter, sticking it in a milk carton and cranking for a 2 seconds. 1/4 cup of diesel squirted out so it looks like the lift pump is good.

When I tried to bleed by manually actuating the lift pump I never got anything to happen, even when I rotated the crank several times trying to find the spot for the cam. After doing that there was way more air in the system than usual and I had to bleed for a few intervals of 5-10 seconds before getting straight diesel.

So what's the next step? How do I check the fuel lines for air coming in. Which lines or connections could contribute and which are not pressurised.
Obviously everything from the fuel line coming from the tank to the return line going to the IP. What about the return line from the IP to the tank? Fuel filler hose and breather hose?

I could bypass the hose going to the lift pump by running a line straight to a gas can but I'm not sure I'd want to test drive the truck to see if the diesel supply line is the issue. I've read John's suggestion to remove line going to injection pump and crank without stop solenoid as well. I guess I'll start with those two tomorrow morning.

I know several other things could lead to lack of performance like timing, turbo clogged somewhere, turbo intake hose collapsing, etc but the fact that I'm getting tiny air bubbles out every day leads me to believe that it's a fuel issue.

 

[javelinadave]

I have seen this before. Swap out the spin on fuel filter and look if the old filter seal looks deformed. Also be sure the mating surface on filter holder is clean.

 

[JimC]

Are you getting white smoke? That’s a common symptom of under-fueling. Also, just check to make sure your accelerator cable is operating the throttle on the pump through its entire range...

 

[Napalm00]

Steps id do to make sure its not the lift pump.

1. remove banjo bolt from injection pump input
2. remove stop solenoid wire from back of injection pump
3. put fuel line from injection pump into a bucket
4. crank engine with starter
5. observe powerful flow from fuel line
6. manually actuate the lift pump you may have to move the crank position
7. observe power pulses of fuel into the bucket

If you dont get powerful fuel flow on both manual cranking and starter cranking its the lift pump. You have the classic symptoms of a bad lift pump.

• Poor high speed performance
• hard starting

on this note if you still have ANY black nylon fuel line, plan to remove it. it def allows for easy air to get in. Buy a bunch of 30r9 5/16 fuel hose and worm clamps, replace all of it AND re route the lines so you no longer have the double loop that traps air on the early trucks. you may need to block off one of the filter ports

optimal fuel flow:

1. tank output
2. lift pump in
3. lift pump out
4. filter in
5. filter out
6. injection pump in
7. injection pump out
8. tank input

see this thread: https://nas-row.com/index.php?threads/200tdi-fuel-system-refresh-and-stainless-hoses.1347/

 

[lcdck]

Are you getting white smoke? That’s a common symptom of under-fueling. Also, just check to make sure your accelerator cable is operating the throttle on the pump through its entire range...

No white smoke unless I’ve disconnected one of the fuel lines to check something. Then it goes away as soon right after I open the bleeder on top of the fuel filter housing.

 

[lcdck]

Steps id do to make sure its not the lift pump.

1. remove banjo bolt from injection pump input
2. remove stop solenoid wire from back of injection pump
3. put fuel line from injection pump into a bucket
4. crank engine with starter
5. observe powerful flow from fuel line
6. manually actuate the lift pump you may have to move the crank position
7. observe power pulses of fuel into the bucket

If you dont get powerful fuel flow on both manual cranking and starter cranking its the lift pump. You have the classic symptoms of a bad lift pump.

• Poor high speed performance
• hard starting

on this note if you still have ANY black nylon fuel line, plan to remove it. it def allows for easy air to get in. Buy a bunch of 30r9 5/16 fuel hose and worm clamps, replace all of it AND re route the lines so you no longer have the double loop that traps air on the early trucks. you may need to block off one of the filter ports

optimal fuel flow:

1. tank output
2. lift pump in
3. lift pump out
4. filter in
5. filter out
6. injection pump in
7. injection pump out
8. tank input

see this thread: https://nas-row.com/index.php?threads/200tdi-fuel-system-refresh-and-stainless-hoses.1347/

I changed the fuel filter housing to the later 200/300tdi housing so I have a fuel in from lift pump and a fuel out to IP only.

The hose from the tank to lift pump is the hard black line so I’ll replace that with the rubber hose and clamps. I have plenty of that around. The only other hard black lines are the ones going to fuel filter and they’re new. Guess that doesn’t mean they’re good though.

Oh, and start is easyright away. No hard start, no stumbling, just feeling under powered.

 

[Napalm00]

make sure to use at least 30r9 any thing lower rated 30r3/5/7 is not diesel rated and will swell.

 

[Napalm00]

have a boost/egt gauge ? checked all the intercooler clamps ?

 

[lcdck]

No boost or egt. On the list though. I’ll double check the intercooler clamps and hoses but I was pretty fastidious with those during install.

 

[Napalm00]

Is the oil feed stand off for the turbo that sticks out of the intake manifold snug? That is another place for common boost leaks.

 

[lcdck]

see this thread: https://nas-row.com/index.php?threads/200tdi-fuel-system-refresh-and-stainless-hoses.1347/

Wow. Okay.

 

[lcdck]

Is the oil feed stand off for the turbo that sticks out of the intake manifold snug? That is another place for common boost leaks.

Hmmm. I’ll look tomorrow. I have a tiny, literally pin-hole size puncture in the boost pin diaphragm. It wouldn’t cause the air getting into the fuel system but could be making the turbo/fueling sluggish at high speeds, no? The weird thing is that the revs are even, no stumbles, truck moves well until around 40-50mph and then feels weighted down. I’m thinking I may have multiple problems working against me.

 

[Napalm00]

A pinhole in the boost pin diaphragm would allow boost pressure to pass through the diaphragm and out the vent. Instead of pushing the diaphragm down like it's supposed to allowing you to increase your fueling rate. It's directly related to how much fuel your injection pump puts out in each duration cycle.

It's most likely directly related to your issue

 

[lcdck]

A pinhole in the boost pin diaphragm would allow boost pressure to pass through the diaphragm and out the vent. Instead of pushing the diaphragm down like it's supposed to allowing you to increase your fueling rate. It's directly related to how much fuel your injection pump puts out in each duration cycle.

It's most likely directly related to your issue

I gotta say, it feels more turbo related than fuel due to the fact the the engine revs very smoothly, even under load. I hope the fuel pin that runs along the boost pin in the injection pump isn't stuck. I'm about to start checking the fuel lines anyway and on my way to pick up a new fuel filter as well. I'm still getting very small bubbles coming out for a second when I bleed it while idling in the morning.

 

[lcdck]

Old lift pump was pumping out diesel during cranking but not using the priming lever. I replace line to lift pump with new 5/16th hose, installed new fuel filter, checked connections to fuel filter and IP. Basically the same issue except my new lift pump, from RN, is spewing diesel from the underside somewhere. Grrr.

I have another new lift pump I'll swap and if that doesn't work I'm out of ideas. Maybe back to the original for now and suffer with 55mph this weekend.

 

[erover82]

Did you fix the diaphragm leak to rule it out? A dab of cyanoacrylate glue should serve as an easy temporary fix.

 

[lcdck]

Did you fix the diaphragm leak to rule it out? A dab of cyanoacrylate glue should serve as an easy temporary fix.

No. But I was thinking something like that.

I did manage to fix the air leak. I’m not sure if it was the hard nylon pipe from the tank, the somewhat rusted fuel filter (need to install a sedimenter), or the lift pump but the second spare lift pump, new filter, and new hose seems to have fixed it. Truck is running much better. Easily getting past where it was feeling limited before. I still think there may be a turbo or boost issue. I checked the intercooler connections and the intake hose from the air cleaner housing. All seem good and the turbo is definitely sucking in air under strong throttle as I can see and feel the hose moving (but not compressing to the point of blocking air).

I’ll try a little super glue on the pin hole and see what that does.
I’m having a hard time finding a new boost diaphragm for sale anywhere other than eBay in the U.K. prices are quite steep after shipping.

 

[lcdck]

Something I'm just discovering now: pre 200tdi LT77s have a lower gear ratio in 5th than the ones that came with 200tdi's (.8413 vs .77). By my math I'm going to be down about 5mph at around 3k rpm. So if people are reporting 65-70mph with the later LT77's at 2800-3000 rpm, I'll be doing 60-65 (roughly) at the same rpm. That's roughly where I think I am now, though I'll find out tomorrow on a highway drive. Maybe it's time to install the 56A LT77 that's just sitting on my garage floor waiting to be cleaned and sealed. Or a stumpy R380.

 

[Mirrajumper]

Did you remove the boost pin to check,clean and adjust?

 

[lcdck]

Yes. The problem is fixed. It seemed to be a combination of bad lift pump, fuel lines, and a pin hole leak in the boost diaphragm. It’s running as it should now. I will install a stumpy R380 transmission in the fall to lower the RPMs in 5th gear.