Surging

was running great yesterday.
now its surging at idle and low rpm. Runs fine on highway. Just had a 1/2 hour highway road trip and back. did a little research. i did break out the glass ball on my return line 3 months ago. (as per sugestion on another thread) I am running wvo mixed with diesel, I did turn up the IP a couple of months ago 1/8 turn.


[media]http://www.youtube.com/watch?v=D7rBD2xg4Ms[/media]

The 6.2 pump does not like anything but diesel. Its prob ****ed.

So are you saying that the surging during idle, and running strong on the highway is a symptom exibited by ****ed injector pumps??? Is that what they do???? or is this hypothisis based on the fact that I stated im using wvo in my fuel.?

Remember back when gasoline engines had distributors. points and such? A little bit of dirt or crud inside the cap, on the rotor or points made the engine idle bad. The more crud or out of spec the points got, the worse it would idle, start and eventually stumble going down the road. The only fix was to clean or replace the parts and re calibrate them.

The IP on a 6.2 is both a fuel delivery device and the timing device. It has way tighter tolerances than any distributor. If you have good fuel psi to the injection pump, then the problem is just about for sure your IP.

Adding to the difficulty is your fuel. Yes, you might not have filtered your WMO good enough and that caused the pump to go. Or, your pump is 25 years old and it needed a rebuild no matter what fuel you ran.

If you want to prove to everybody that your fuel is not your problem, run 3 or 4 tanks of pure diesel, insure the tank is clean, put on a new IP, run another 3 or 4 tanks of pure diesel, record your performance and then switch to your home brew. Post up what you find. As it is now. You are running experimental fuel in a 25 year old engine of unknown mechanical condition. You are the test engineer and none of us can do much more than what we already have.

Gremlins! Today I went to go work on my surging problem... and Its running normal now. ??? I drove it a little and she is running right. I drove out to Knob creek machine gun shoot yesterday mostly highway, drove 70-85 mph all the way there. was surging when I got there. and drove home and took the video. Just for fun here is todays video.

[media]http://www.youtube.com/watch?v=pKXjtZaMt_k[/media]

kentuckycucv said:

.... drove 70-85 mph all the way there.

Click to expand...

If your running these speeds when the truck wasn't designed for it, I would say the IP is crapping out.

Pull the top cover of the injector pump and look inside. Are there tiny black specks everywhere? If so it is the interal rubber failing.

really?? My truck cruises nicely with the speedo on 75 - 80 this is a m1009 not m1008. The surging stopped I need to go back out to the Knob Creek machine Gun Shoot so I guess im going to try and burn up some more of my home brew fuel on the hwy... I will let you guys know when or if the IP craps out on me. i was hoping that some knowlegable person would know what the surging is caused from. My studies on the internet sugests air in the lines. Maybe water in the fuel? I have a water seperator filter before the stock filter, and the water in fuel light never came on and its running great today. it even seems to have more power with the WVO mix than regular diesel.

Looking through your multiple threads on the same basic problem. One finds a common trend. It works great!, it is a piece of crap, I changed a bunch of stuff, it runs great, it is a piece of crap, repeat.....

You posted up asking for help. Changing filters was discussed before and ensuring the fuel system is intact and functional. We can only guess so much as to what the problem is based on what you report to us has been done. The -20 has a great section about how to diagnose issues as well if you don't like our answers.

I am not stating your fuel is better or worse. Just that the less variables when a problem is present, the easier it is to fix. Fuel is an easy variable to make right. My multifuel ran great for 400 miles one day. I had just put in new filters the day before and was flat towing something. We topped off on fuel and 5 miles later, I couldn't get out of 1 low. Drained the filters and all kinds of junk came out. I made it a mile before the same thing happened again. 5 cycles of draining and maybe a mile covered. I had been running WMO all day. We topped off at a truck stop with a high pressure hose. It stirred up all the settled crud from the bottom.

Could your problem just be filters? Sure. Should you change it out again and see if it helps? Yep. You keep posting like you have done all of that though. The only thing left is the lift pump and IP.

If you have stock 31 inch tires on the truck. 80 mph is 2742 rpm. That is way past the most efficient speed for a non turbo diesel engine. Most of us consider 2500 a good self imposed red line for long lasting engine mechanical life.

Have you swaped out for electric fuel pump yet ... abandon all hope with the mech. if you are running crap ... sound like you notget enough fuel until the the IP pump sucks it though at the higher RPMs

Southdave I see you are TDY, are you at Crane NSWC?

mine does the same thing runs good until warmed up. was told its some kind of timing mechanism in the IP that goes bad

Truck seems to have power, runs good but I took it out for another 30 miles on the highway, got her up to 85...maybe 90 When i got off the freeway it was surging again. if i accelerated , a little brake torque it leveled out. I drove it home and didnt push it so hard. It was surging when i got home, but not as bad. let it sit for a couple hours wentt to start... and the surging stopped. i think i may be getting air in the line. I bought some transparrent hose and put it on the return line. I will try and duplicate the surging andsee if it has air bubbles, then i will know.

I drove today on the highway, didnt use my lead foot, drove great, seems to have power.. No surging when I got off the highway. got home and opened the hood and checked out my see thru return line. Guess what? Bubbles
Air bubbles. So i think at the higher RPM I had accumulated air in my IP. So now I need to find the sorce for the air.
Since you guys like pictures so much ...I took another video.
Any Ideas thoughts?
[media]http://www.youtube.com/watch?v=gnf89fRGUlk[/media]

If you are getting air bubbles and it is not surging wouldnt the surging be caused by somthing else?
Also check this out.
Hard starting CUCV's

Found this on another site. YMMV

Symptoms of an air leak include surging, hard starting, no start, rough running, rough idle, and stalling.

These methods should not be used on trucks with very rusty fuel tanks, as it is possible to blow a hole in the tank.



To bleed air (or old fuel) out of the system on early models (1982-1984):


Hook an air compressor hose into the return line at the injection pump (IP). The line you want is the rubber one that goes into the front of the IP. Alternatively, you can stick the air hose into the filler neck, but that is not as effective. You can also modify a fuel cap with a valve stem off of a tubeless tire and use an air chuck to supply the air, which works good. Whatever way you choose, the next step is to loosen the fitting on the outlet side of the fuel filter. Loosen it enough that fuel will come out readily, but don’t take it all the way off as you will need to be able to tighten it fairly easily. Put a pop bottle with a funnel stuck in the neck under the fitting to collect the fuel. With the fuel cap on tight, turn on the air to about 4 psi. Give it some time to fill the fuel tank. Fuel will start to run out of the fitting and into the pop bottle. When the pop bottle is about full, tighten the fitting. Then turn off the air. Disconnect the air line, wait for any remaining pressure to bleed out of the tank, and then reconnect the return line to the IP. If you used the modified fuel cap or the hose in the filler neck, you can ignore these last few steps.

Once you have bled the air out of the system to that point, you may need to crank for a while to get it to start. It is not necessary to loosen injector lines to bleed the system to the injectors on the 6.2. Simply crank until it starts. You will need to do this in several cranking sessions of about 15-25 seconds in length so that you do not burn out the starter.




To bleed air (or old fuel) out of the system on 1984 and later models:




These trucks were equipped with a combination fuel filter/water separator/fuel heater ("square" filter). If your truck is equipped with a "round" filter, see the procedure for early model trucks.

Hook an air compressor hose into the return line at the injection pump (IP). The line you want is the rubber one that goes into the front of the IP. Alternatively, you can stick the air hose into the filler neck, but that is not as effective. You can also modify a fuel cap with a valve stem off of a tubeless tire and use an air chuck to supply the air, which works good. Whatever way you choose, the next step is to open the air bleed valve. It is located on the top of the fuel filter mounting block. There is a hose fitting right next to it. Hook a hose onto that, and run the hose into a pop bottle (this will collect whatever fuel you bleed out). With the fuel cap on tight, turn on the air to about 4 psi. Give it some time to fill the fuel tank. Fuel will start to flow out of the bleed valve and into the pop bottle. When the pop bottle is about full, close the bleed valve. Then turn off the air. Disconnect the air line, wait for any remaining pressure to bleed out of the tank, and then reconnect the return line to the IP. If you used the modified fuel cap or the hose in the filler neck, you can ignore these last few steps.

Once you have bled the air out of the system to that point, you may need to crank for a while to get it to start. It is not necessary to loosen injector lines to bleed the system to the injectors on the 6.2. Simply crank until it starts. You will need to do this in several cranking sessions of about 15-25 seconds in length so that you do not burn out the starter.




To find an air/fuel leak:




Utilize air pressure to test your fuel supply system for leaks. The procedure for connecting the air is the same as the one used to bleed the system, however you don’t loosen the fitting at the fuel filter (on 1982-1984 models) or open the bleed valve (on newer models). Once you have the system under pressure, crawl under the truck and look for fuel leaks (it might be a good idea to wear safety goggles when you do this). Work slowly from the fuel tank to the injection pump. You need to look very closely, because any leaks are likely to be very slow leaks. Check every connection, every hose, the fuel pump, the fuel filter(s), and the tank switch (if the truck has dual tanks). In short, check everything. When you think you’ve checked everything, go back to the fuel tank and start over. A good thorough inspection should take about fifteen or twenty minutes. Anything that is just barely seeping fuel needs to be repaired. Fix any leaks, test it again, and when you get to the point where it no longer leaks, bleed the air out of the system. Replace the rubber hose on the return line with a clear hose before you start the engine. Start the engine and let it run for a while. If it runs good, take it out on the road for a short distance. Then look at the clear hose and look for any bubbles. If there aren’t any, you are probably in good shape.

If everything looks good, but the engine won’t start the next morning, you probably need to replace the fuel pump. Replace the pump, bleed the air out of the system, and you should be in good shape.

The surging happens when there is more air bubles comming out the return line. Also I can pinch the return line and the surging stops. I dont know if thats bc the return valve is too wide open with the \glass ball busted out or if its the air.
I only get air after i have been driving it.... Should I buy a new Valve with the glass ball or go with a new fuel line and electric fuel pump?

Same symptoms intermittent surging stalling hard starts will run great a few days then do it again. Changed filter bled and a leaking fuel line fixed pulled check valve no chunks a little varnish cleaned looks good . Where do I look next?