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Fuel Pressure/Filter & Transmission Issues


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Couple items I am having trouble with.  Have an 01 with 190,000.  50hp injectors and a newish DTT Assassin lift pump.  Original VP as far as I know.  I do run 2-stroke at 1oz/gallon. 

 

Ever since I installed the assassin lift pump I have been having trouble with consistent fuel pressure.  For those that don't know the DTT is a mechanical fuel pump that drives off the harmonic balancer, so in theory, as rpms increase so does fuel pressure.  I have yet to see this happen.  Right now I will idle at 17psi and drop to 10psi when I get into the pedal.  I changed out the fuel filter a couple times and when I do the problem goes away for a day or so, then returns.  I was curious if anyone else running 2-stroke had seen any issues with pressure drop across their stock filter?  I am thinking about trying a Wix filter, but I hate to keep dumping $20 into filters.  I have been through 2 or 3 already this summer trying to troubleshoot and only put on about 5,000 miles.

 

2nd item:  The other day I was cruzing down the road about 50mph and the tranny seemed to shift into neutral for a second, then back into OD.  I was able to get it to repeat sporadically, but it seemed to be when I was under a very slight acceleration.  It also happened this weekend when I was pulling the camper out, but I'm pretty sure it was in 3rd gear.  It seems to shift to neutral for a second, then back into gear.  Tranny was flushed within last 20,000.  Fluid level is ok, but I will check again.  I adjusted transmission bands last summer for the first time.  Any thoughts?

 

Thanks.

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I have the Fuel Boss installed on my truck which is also a mechanical pump. When I first installed it my fuel pressure dropped to 5 psi.  There was debris from the fuel line lodged in the bypass valve.  That valve is supposed to keep pressure constant around 18psi, unless it is stuck open.  My fuel pressure does a great job maintaining that pressure without any fluctuation whether it be at idle or WOT.

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Well everyone has already mentioned everything to look at. On your fuel system the bypass valve is stuck open and your alternator may be the cause of the Trans issues. Check the alternator for AC noise to see if the field has failed.

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The only way to test it is to hook it up and turn it on. The reason they put out AC noise is because the brushes are or part of the armature are contacting the case. Hence the reason you have to hook it up and turn it on. Sorry Joe.

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I think the fuel pressure drop is to be expected depending on how your fuel system is hooked up. If you are pulling the pressure off the pump, and have a big line kit to the stock filter, and not from the filter to the pump, you will see a drop in pressure when at WOT or pulling under load. As long as the pressure isn’t dropping under 10LBS you should be fine. I think this characteristic diminishes greatly when the stock filter is eliminated and the big line kit runs straight to the pump. 

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If the place you get one from has the machine and is willing they may put it on the tester to find out what the AC voltage is.

There is a place in Clackamas that does their own rebuilding inhouse. That might be a good bet. I'm sure they could easily test the alternator you intend to buy. Note to self. Hey, maybe it would be a good business venture to buy all the a/c noise alternators and market them to guys with stick shifts.

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There is a place in Clackamas that does their own rebuilding inhouse. That might be a good bet. I'm sure they could easily test the alternator you intend to buy. Note to self. Hey, maybe it would be a good business venture to buy all the a/c noise alternators and market them to guys with stick shifts.

I don't know if you would have enough cash for that venture!! A good rebuild shop is the best place to get an alternator if you can.

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I know very little except to not trust Dodges fuel system. So I have 1/2'' lines all the way with a prefilter to catch the bigger debri before it gets to the pumps inside workings. I like a water separating prefilter so the pump cannot break up the water droplets and emulsify them to a point that the finer factory filter cannot separate those out. Letting any water thru is bad news for a number of reasons.

At a 190,000 miles I think you had better drop the tank and rid yourself of the factory screens in the fuel module and rid yourself of that little cylindrical plastic housing inside the module that holds added screening. Do you know if you have an old intank pump still there you are pulling thru?

If you modify the fuel module for better flow, no screens and such you may as well change to a 1/2'' drawstraw from Vulcan performance.

Anyone here might know... but, wouldn't the trans speed sensor cause your problem with the trans?

Also the amount of AC noise coming off the ALT. is supposed to remain very low. Can't remember but, there is an article on how to check for that under articles in this forum. Batteries and all connections need checking as well, but when checking ALT noise you need one of the expensive Fluke type volt meters as most VMs won't show it and aren't accurate enough to do that.

BTW, your fuel pressure should never go below 14 p.s.i. that is the least that holds the return flow overflow valve all the way open in order to keep the vp at long lasting cooler temperatures.

Also could the assassin pumps' belt be getting oil and slipping from the breather bottle draining oil onto the belt in front of the engine? There is a mod in articles to get it to throw the mist oil to the rear of the engine.

Good luck... hope this is some good anyhow.

Rember no truck is perfect but being on this forum is the closest you will ever get to that.

Edited by JAG1
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I missed the part about your transmission. Stupid question, but did you check the fluid? When they get low the will suck air when you turn or the level sloshes. Other than that it does sound like the speed sensor in the side of the transmission. What is probably happening is the transmission is actually down shifting and then up shifting again. Something to try is see if you can figure out a way to tighten the connections where the harness plugs onto the sensor. If you decide to change it it is real simple. Just unpulg the sensor, unscrew the old one, screw in the new one, then plug the harness back in. You will spill a little trans fluid, but not enough to be a problem. BTW, here is what the sensor looks like: 1979-05109319-1062453.jpg

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Thanks all for the thoughts and comments.  On the fuel pressure, I do have a 1/2" draw straw installed and I removed the in tank filter screen a couple weeks ago.  I left all of the plastic housing, just pulled the screen out.  I tried to run a water/fuel seperator filter right out of the tank, but with all of my fuel pressure issues I took it off.  I don't think it has to do with debris in the pressure valve.  Usually when that happens the pressure is really low at idle and will build to full pressure as I get into the throttle.  I hadn't looked into modifying the stock fuel canister to allow for the extra flow.  I will do some looking around on the forums for some modifications.  

 

I did check the transmission fluid, but I just found out a couple days ago I was supposed to do it in nuetral, not park.  So I will check it again today.  I am going to run to town and pick up a speed sensor just in case and will swap that if my tranny fluid level is good.  

I hadn't heard of the alternator issue before, so I will double check all of the battery connections and wiring.  I think I know of a shop in town that can test the alternator.  

 

Thanks again.  Will post back once I try a couple things and hopefully get the issues solved.

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Ever since I installed the assassin lift pump I have been having trouble with consistent fuel pressure.  For those that don't know the DTT is a mechanical fuel pump that drives off the harmonic balancer, so in theory, as rpms increase so does fuel pressure.  I have yet to see this happen.  Right now I will idle at 17psi and drop to 10psi when I get into the pedal.  I changed out the fuel filter a couple times and when I do the problem goes away for a day or so, then returns.  I was curious if anyone else running 2-stroke had seen any issues with pressure drop across their stock filter?  I am thinking about trying a Wix filter, but I hate to keep dumping $20 into filters.  I have been through 2 or 3 already this summer trying to troubleshoot and only put on about 5,000 miles.

 

From what I've heard about DTT Assassin fuel pumps they have issues with the regulators either sticking, springs wrong strength, debris in the regulator, etc. 2 Cycle Oil will not change fuel pressure if used properly at 128:1 ratio. Trust me its not the filter causing this pressure drop it solely the lift pump.

 

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I was informed that the best way to check the fluid was with the transmission in drive with the engine running. Make sure you have a great parking brake or someone you can trust holding the brake pedal!!

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