Frybrid 1996 Cummins Conversion Studder

[Trilogy]

I just completed the first phase of the 96 Cummins conversion (Frybrid Kit). The first step is basically replumbing the fuel system but no VO yet and the engine runs great and at the moment (1 full day of driving) showing no leaks. Only problem is on start-up in the morning the truck fires up perfectly but then 5-10 seconds into running I get a brief studder in the engine. If I do not give it gas the motor will stall and then after a few rough starts with the fuel pedal down she will fire up and run perfect. Now if I give it gas as the studder starts it does not take much but will push through the studder and then run great for the rest of the day.

The studder does happen on every stop start of the engine.

First guess is air in the system, but showing no leaks and the fact that it runs so clean and smooth after the studder if the system was leaking air it should have other issues during normal operation or is that not right?

After re-plumbing the system, what is the best way to purge the lines, as the normal bleed valve on the top of the fuel filter has been removed?

Is it possible that there was so much air in the lines (due to the replumbing of the fuel system that I should just keep driving for a couple of days and see if it gets better?

Any info on how to fix or if anybody had a similar issue at install would be helpful as I would like to resolve it now, before completing the fuel install of the VO system.

Trilogy

[Boise_Wannabee]

isn't hooked up to anything. It needs to have the VO on the other side of the valve, or it will suck a bit of air into the system.

Nice work, you're almost converted.

[Trilogy]

I see, that does make a little sense.

One more quicky, the VO return line that is capped off right now does have some diesel going into it, is it normal for some diesel to return into the VO return or is this also because no VO is in the valve, thus no resistance?

thanks, hoping to finish this thing off this Saturday and be up and running. I appreciate the support, I will say that re-plumbing this thing was very similar to yoga, only add a little torture and a lot more cussing.

Ben

[moparman13045]

I had this exact same problem recently on the exact same engine, and I am 99.9% certain you do have an air leak on the diesel side, somewhere, I am guessing that you have redone the fuel lines so that the diesel is pulled from the tank through the diesel fuel heater, then through the filter and into the lift pump. It also does not matter (that I am aware of) if you have the solenoid hooked up to the VO side, it still should not leak by, if it does I assume that it is faulty. Back to your studder problem...you will not see your leak most likely if it is an air leak before the lift pump due to the fact that you are pulling fuel through there not pushing it, i.e. the pump is creating vacuum at the fittings, not pressure. If it is after the pump, you should see some kind of fuel leak. Make sure that you use a healthy amount of pipe thread sealant on the connections, and make sure that they are all tight. I know it is a pain to get to them, maybe removing the starter will help, it did for me. I don't know why you have diesel in your return line, you shouldn't. The hoses are attached on the correct ports right?

As for bleeding the system, if you have routed the lines the way I described above, I found that bleeding the system is easiest at the injection pump inlet.

I hope that this will help you.

[Trilogy]

OK, I will check and tighten real tight the connections prior to the lift pump and hope the studder fades, keep the fingers crossed (mainly that I don't pull out my back contorting to tighten that connection at the top of the pre-heater).

Just quadruple checked and I am hooked up to the right ports. Silly question, and I will check this tomorrow, but is it possible the valve is switched up? I will disconnect tomorrow #2 port on the return and if it is dry I know the numbers are tweaked.

Odds are this won't be the case and the valve is bad. What is the best way to handle that, post on the forum to Chris or try and get through via the phone?

Just to ask, if it is a small amount of diesel leaking through to the VO return, could I still hook up to VO and allow a little diesel into the VO or would that be disastrous?

[cgoodwin]

The valve is not air tight (Called "bubble tight" in the valve industry) so you will want to have a fluid on all sides of the valve to prevent air entering the system. If the valve has an issue simply send an email with "Warranty" in the subject line and I will address it first.

[walexa07]

OK, I will check and tighten real tight the connections prior to the lift pump and hope the studder fades, keep the fingers crossed (mainly that I don't pull out my back contorting to tighten that connection at the top of the pre-heater).

Just quadruple checked and I am hooked up to the right ports. Silly question, and I will check this tomorrow, but is it possible the valve is switched up? I will disconnect tomorrow #2 port on the return and if it is dry I know the numbers are tweaked.

Odds are this won't be the case and the valve is bad. What is the best way to handle that, post on the forum to Chris or try and get through via the phone?

Just to ask, if it is a small amount of diesel leaking through to the VO return, could I still hook up to VO and allow a little diesel into the VO or would that be disastrous?

In my opinion, your problem has already been nailed down..........it is the valve leaking due to the vo side not hooked up. If it was a large leak you would notice it much more. I would complete the installation according the the manual, and if you still have the studder problem after getting the system completely hooked up, I would then investigate other possibilities.

Waylan

[moparman13045]

I would doubt that the valve itself is bad. The Frybrid components are of very high quality. Sorry if I provided you with any incorrect info, I didn't realize that they could potentially cause an air leak without being hooked up on the VO side. So it is a good idea to try and hook up your VO side and then see what happens.

By the way it is okay to have a little bit of diesel mixed into your vegetable oil tank, it will not hurt anything that I am aware of.

Hope that you get that hooked up soon, its a great running vehicle just on diesel, but even better on vegetable oil.

[Trilogy]

Once the system was hooked, studder went away thank goodness. Thanks for all the input everybody. Running on VO, all is working well...120 miles and keeping a log journal so I will keep all informed.

I have noticed that measuring the temp on the coolant at the temp sensor I am reading 160 and higher well before the temp sensor is kicking in. Having read about the thermostat I will try and switch to a 195 degree thermostat and see if that causes a faster switch over to VO.

I will let all know. Right now burning a whole tank of SVO and then if all is well I will start burning the 200+ gallons WVO I have stocked up and filtered (This pile of course is making the wife very happy).

Once again thanks everybody and I will be in touch.

[dougk]

I was going to keep a log of my miles too but it didnt work for me very well. I kept all my miles up to about 1000 and then I got sick of taking down all the miles I put on veggie. It seemed really cool and I wanted to see how much money I would be spending on diesel but then I took it for granted and now just go and forget about how many miles I have on veggie. I have a rough estimate but I admire folks who can stick out the intire journey. Good luck on keeping all your miles.

DK