Injection Pump Issues and Adjustment Procedure

[Zion]

Recently, I was lucky enough to buy a 1984 6.9L off of a buddy for a $1000. The POs he got it off of had the pump turned all the way up. As it stands right now, the truck is having some issues starting, idling, and maintaining power. I know air-intrusion is present, so I’ve already gotten a return line kit and plan to install it today, but I’m starting to wonder about the IP’s health. The truck hard starts every morning, typically popping off for a few seconds, stalling, then reviving with a rough idle after one or two more starting cycles. The idle ranges from an unsynchronized, but not awful, drum line to an aggressive lope. Once warm, the idle clears, but it will continue to lightly smoke from the exhaust. When driving, it’s pretty gutless, even by IDI standards. Some mornings, I’ll get about a half mile into my commute with great performance before the engine suddenly reduced output.
making with the return line kit, I’d like to turn down the fuel pump. I’m aware of how to adjust the fuel, but if the pump is turned all the way up, how do I gauge how far to turn it down?
It has the stock lift pump, so that may be a component to this issue, but I suspect that the IP is not in great condition. I’ll replace the fuel filter today, and have heard that either ATF or Seafoam is advisable for cleaning up the injection system. I’ve got a friend that has a few IPs and some non flow matched injectors I could get without breaking the bank, but I’d appreciate some input/directions for identifying if the IP is my issue.

 

[chillman88]

Timing is probably more your issue than anything, other than the obvious problem of the air intrusion.

Get the air intrusion fixed, then if you don't have a meter, or anyone close who does, try bumping the timing about a dimes thickness towards the passenger side. If no change, go a little bit more. Fiddle with it a few times and I'd bet you'll get to where there's a noticable difference.


As far as the fuel, the best thing I can say is buy a pyrometer. Watch it for a while and if it's too hot turn it down little by little until your EGTs are good.

It's never a bad idea to have a pyrometer on these anyway.

 

[Zion]

I replaced the return lines and fuel filter w/ ATF, and I’m still having some issues. There is improvement, so I’m sure air intrusion was a factor, but it still hard starts/stalls and surges on occasion. I’ve removed an injection pump, but never messed with the timing. I’m assuming it’s done by loosening the 3 9/16th bolts that mount the pump and then rotating it, or removing the inspection cover and 5/16th 12pt, but I’ll be sure to find a write-up before I dive in.

 

[Booyah45828]

If it's a new to you truck, it might just be time for a set of injectors and a pump. Neither one is a million mile part. For starters you can verify fuel pressure and that you don't have air intrusion, maybe some fuel additive and atf in the filter, but anything more then that on a questionable pump and injectors is wasting time IMO.

Unless the timing is out a mile, it won't cause hard starting, no starting, loping, or surging.

 

[chillman88]

Next time it sits all night remove the fuel filter and see if it's still full. You'll know because if it's full it will leak as soon as you loosen it.

Just the three 9/16 nuts get loosened to set timing FYI.

You could have an IP problem, but those are classic symptoms of air intrusion. I'd really hate for you to buy a new IP and injectors just to find out it's still doing it.

FYI if you decide to replace the pump, do some research. There's lots of places to get them, but only a few that have proven themselves over and over to do it right, with lots of places selling garbage.

 

[gnathv]

If you do try adjusting the timing, only adjust with the motor off. Tighten the bolts between adjustments, don’t try to leave loose.

 

[ISPKI]

Some testing is definitely in order. Just replacing the return lines doesnt guarantee that you eliminated the air intrusion. I know I have replaced the caps, lines, orings, and clamps and still had one or two leak. That return system is probably one of the weakest links in the IDI design.

I had hunted air intrusion for months on my previous rig. I ended up installing clear C-210-A lines for all the soft lines on the truck which allowed me to pinpoint where the air was leaking in. Ended up finding a tiny trail of bubbles at the barbed fitting on the top of the IP cover.

 

[Zion]

After spending some more time looking over the truck, I believe it may be the stock lift pump and/or tanks. The lift pump, although it may have been replaced at some point, is still the stock mechanical. Even if I let the truck sit for a couple nights, it’ll fire up first try, but then stall within seconds. As far as the tanks are concerned, only one currently sends fuel, and the gauge has faulty readings. Sometimes it won’t read full after a fill-up, sometimes it stays at a quarter tank for days. I wouldn’t be surprised if the feed tubes and floaters are gonzo. Even with the fuel issues, it is surprisingly reliable, but I think it is in my beat interest to focus myself on the lift pump and tanks for right now.

 

[ISPKI]

After spending some more time looking over the truck, I believe it may be the stock lift pump and/or tanks. The lift pump, although it may have been replaced at some point, is still the stock mechanical. Even if I let the truck sit for a couple nights, it’ll fire up first try, but then stall within seconds. As far as the tanks are concerned, only one currently sends fuel, and the gauge has faulty readings. Sometimes it won’t read full after a fill-up, sometimes it stays at a quarter tank for days. I wouldn’t be surprised if the feed tubes and floaters are gonzo. Even with the fuel issues, it is surprisingly reliable, but I think it is in my beat interest to focus myself on the lift pump and tanks for right now.

Yeah old lines, old filters, old lift pumps are all cheap replacements with a bit of elbow grease. If your tank runs low enough, the pickup can suck in a bit of air and that can cause all kinds of issues. I actually stranded my truck at the head of my driveway when I went to back in with a low forward tank. Fuel lurched forward and it sucked up some air, stalled the truck out and couldnt restart it without cracking all the injector lines and cranking the air out of the system.

 

[Big Bart]

Some thoughts -

Worry less about the fuel tank they usually do not effect the running part but keep in mind -
1) All of us suffer from dying fuel gauges, I just set my tripometer to zero each fill up and after 120 miles switch tanks, 120 miles later I refill. Mileage will vary so you might find 100 or 140 is more for you.
2) There is something call the shower head on the fuel line pickup in many of the tanks, when it falls off your suction line is not at the bottom of the tank, now it is pulling at 3-4 inches off the bottom, so you run out of fuel before the tank is truely empty.
3) Your fuel tank selector valve hower can mess with you. They start to stick and can stick half on half off or inbetween tanks. (Basically all off.) Causing no fuel, limited fuel, etc. So always keep that in mind when looking a fuel supply issue.

Air is the enemy, so you have to track it down. So many places and so many lines that can leak. Even the o-rings for some of the parts on your fuel filter system can cause air leaks. Many articles here on Oilburners on what to look for.

IP's are tough to diagnose. You really have to send them to be bench tested to know much about their health. But start with getting the air intrusion resolved. Pump timing is SOOOOO important. Get your timing set with a timing kit or go to a garage that has one. (Many mechanics don't have one so they just time by test drive, that does not work.) Your timing will effect hard start, power, overheating, fuel consumption, etc. You can find a guy on E-bay who sells new miltary Tech Time pump timing kits for around $225, some state he will take an offer of $180. Again search some articles lots of discussion on how to set. One of the ways you know the timing is pretty close (Or on) is when you start the truck it starts right away (Provided your glow plugs work.) and it is very loud and clackity, then over the next minute or two it gets quieter. (It does require your IP advance to work too.) However that is something you will notice if your timing was off and now set correctly.

Glow plugs -
Glow plugs are also very important on these trucks. If your "Wait to Start" light does not go on with the engine cool or cold for 5-20 seconds, it is not likely working right. On the 6.9's they work differently, so not an expert, I have a 7.3. But if your light goes on and 1 second later goes off with a cold/cool engine, you have an issue. Likely 3 or more bad glow plugs or a wiring issue. Now you will suffer long hard starts, a engine that races up for 2-3 seconds once it does start, and a cloud of smoke. So make sure your glow plugs work. (It can more than just putting new ones in, sometimes that fixes the issue, sometimes it the wiring, controller, or relay.) ONLY USE MOTORCRAFT ONES! Or they will balloon and be hard to get out or break off!

We would all share with you that your first few fixes will likely be a little painful and trying. Just don't give up, keep working the issue till you fix it! Share your issues here and you will get a lot of ideas to check and a lot of good advice about how to fix something once you know what you are trying to fix. You will have those days you want to sell your truck or light it on fire! Take the day off from fixing it and start renewed the next day.

In relation to a 2021 6.7l diesel, these 30 year old diesels are very easy to diagnose and fix. Also you paid $1000! Some guy/gal just paid $70,000 to get a new one out the door! Working you should be able to get $4-7K, so you can dump some good money into your truck, see if you like the truck. If not get your money out, especially right now with new trucks hard to find! The resale market has gone way up!

Welcome to the club!

 

[MrDeLeoCo]

Zion ... Were you able to diagnose and resolve to problem?
I am having a similar issue... UPON STARTUP, I have to keep the engine at fast 2200 rpms while engine surges; When the Temp gauges reaches operating range, the engine settles and idles nice.

1987 F250 6.9L