6.5 wont take fuel when cold
 

I have a 94 k3500 6.5 that I just acquired. My first 6.5. It has 201k miles on it and I don't know the history on it. The truck starts right up and idles but it won't take fuel when I push on throttle. Once the truck warms up well it starts taking fuel and runs great. It usually takes 10-30 minutes to take off. The lift pump looks new and I've overlooked it some but I'm not familiar with it. The truck it kinda rough and I don't want to sink a fortune in it. Please help and thanks

I don't understand description "won't take fuel" if it is running/starting it is taking fuel, anytime fuel delivery is suspect ALWAYS CHANGE the on engine fuel filter in the center rear of the engine as one never knows when you get a bad load of fuel partially or completely compromising fuel flow.

Yours being a 94 is OBD-I electronics so you don't have the redundant power to the lift pump and all coming from the OPS (oil pressure switch) that has a dual role powers lift pump upon sensing oil pressure, and also providing internally a second circuit for dash display of oil pressure, you can have oil press showing on dash but still have a bad OPS feed to the lift pump.


Since you are # ??? owner of this it might be prudent to change this "just because" as an elimination and refresh as they do wear out over time, they aren't that expensive anyway.

If you have a "old school" vac/press test gauge get about 8' of vacuum hose connect one end of it to the outlet/90 deg angle fitting to hose running down behind the water-pump FFM drain valve (brass valve chrome Tee handle center front of the engine) . then snake that hose into the cab taking care to not create a "pinch point" in the hose dead-heading the pressure feed to the gauge, either tape gauge to the windshield for viewing from inside or run hose into cab with gauge .

Start truck and open T handle on valve, this will give you the pressure from the lift pump being supplied to "dirty side " of the filter, if filter is new/clean it will basically also be what fuel is being supplied to the IP.

You should have 7-10 psi at idle with a factory style lift pump if healthy.

If you don't then lift is bad, power to lift is missing, "sock strainer" in tank is plugged, or you have a rotten line/hose and you are sucking in air.

Assuming you idle pressure is correct, take truck for a "road/load test" with gauge connected do some basic driving 3-7 psi is "normal" higher is better, then do some acceleration tests floor it and observe pressure if it drops to 1 psi and recovers quickly then ok but healthy lift should not drop below about 1.5 psi for any amount of time, if it gets to 0 or less than 1 and struggles to recover/supply fuel then fuel delivery is compromised. Most probable offender then would be the lift pump, if going with a OEM pump stay with the AC Delcos, a lot of "JUNK" pumps out there at different part houses Airtex one of the most commonly found one.

Aftermarket pumps need to be Diesel fuel rated with ability to "flow on fail" impulse /plunger pump the IP can pull it's own fuel if lines don't have air leaks and filter is clean, performance will be compromised but you shouldn't be stranded.

Vane lift pumps like the Cummins use may starve you of fuel if the pump stops and one of the vanes blocks either the suction or discharge port of the pumps casing.

One last thought to lack or intermittent lift power, the gnd for the lift pump is on the top of the frame rail more/less below where the fuel filler neck crosses over the frame rail, single 18 Ga black wire with ring lug that needs to be spotless.

Take a piece of emery cloth polish lug to bright clean, then also on frame for clean contact point, then also bolt contact face, after cleaning liberally coat them all with di-electric grease to keep moisture from corroding again, or if you can find it a spray of "Corrosion Block" spray is awesome usually found at boating stores.

Tighten all that up and then use you DVM and check for resistance to gnd 1 probe on the newly cleaned bolt, and other on a good spot on frame or my best confirmation to one of the 2 negative terminals of you batteries, should be less than 1 ohm resistance or whatever your meters lowest resistance capability is when just reading through your leads touching each other.

What I mean by "it won't take fuel" is when I press the accelerator pedal nothing happens, it starts great and idles great it just won't rev until it gets hot. Someone else told me to check the lift pump operation also but I thought If the lift pump was not operating properly then it would be hard to start, but again I'm not familiar with this engine. Thanks for the reply

As long as the line between the IP and tank is fully primed, the IP has ability to pull its own fuel, you may be having a APP issue but lets look into the fuel delivery troubleshooting 1st.

Ok guys have some more info for you to calculate. The coolant temperature sensor didn't fix the problem. I have power on the lift pump after you crank it a few seconds. When it's running the water drain has a good steady stream coming out of it when opened. No service engine light or codes. It is a little stubborn to start when it's cold. It starts and dies a couple times before it will stay running and then it white smokes for a minute or so. I looked it over and checked the wiring today and it all looks good. When it starts it may rev after 1 minute or it may take 20. I stomped the pedal several times with no change. When it starts revving then it runs perfect. Please help me with next step!

A good, steady stream is highly subjective. If it is leaking out vs pouring is a big difference. I checked mine and it was coming out, but turns out it wasn't enough and my fuel sock was clogged. As I had no idea how much fuel should come out, it resulted in a misdiagnosis and more greenbacks out of my pocket. It should fill up a red solo cup under 20 seconds or so.

Mine turned out to be a clogged sock, which fell off in the tank when I removed the fuel sender. I just left it off, but you have to be careful when getting low on fuel.

A new metal top fuel filter is mandatory at this point, and an oil change. Probably wouldn't hurt to have the tranny fluid swapped and a new filter put in. Just make sure they use the good rubber gasket for the tranny, not the cheap cork gasket. Otherwise you will have a friggin tranny leak nightmare.

If possible, straight wire the lift pump just for diagnosis purposes as well. If you splice into the hot wire from one of the power ports on the fuse box, and add a switch, it will help by bypassing the OPS.

Ok great info, I'll check it out tomorrow thanks a lot

Getting closer every day. Took the fuel filter housing off today and cleaned, it was very nasty. Got that all cleaned out and sealed up and checked the hoses for leaks. It has good fuel delivery ti the filter because it was completely empty and I cracked the air bleed valve on top and fired it up, it only took a couple seconds to push fuel out of the top. Truck starts on first try and takes fuel way quicker than before but still not perfect. I did notice something unusual though. When I start the truck it idles at 500. I can press the pedal and it will climb to 1000 then stop. I can play with it a few seconds and it will start revving like a champ, then after it starts working properly it idles at 1000. Seems like the idle may have something to do with my problem? I checked power to the glow plugs also. They have power on them until the light goes off on dash. I read somewhere that they should have power on them for a few seconds after it starts but no sure. I will check it again tomorrow after it sets all night. I really appreciate your guys help I've almost got it road ready thanks to you all.

Make sure all the glow plugs are connected and working properly.

Still think you might have a fuel delivery restriction.

Did you do the lift pump diagnostics I defined above ??? if you don't have a vac/press test gauge......get one......they are like $20 most auto part stores, it is an invaluable test tool.

No I didn't actually test it but it does have power on it and it will fill up the ffm completely empty in just a couple seconds

Well I'm still restoring my truck, almost have it ready for the body shop but I still have a running issue. I have it narrowed down the a fuel delivery problem though. Heres the thing, I can pull out the ffm, dump the fuel out and spray brake cleaner through the outlet to rinse out the screen, it does have some small particles in it usually. Then I can put it back on truck and fire it up and it runs perfect. Takes fuel immediately and idles right and everything. After it runs for a while I can turn it off and let it set, then I'm back to square one, it starts but idles low and won't rev for a few minutes. I can take out the ffm, clean, and perfect again. I don't see enough contamination in the ffm to cause a fuel restriction. Any ideas?

Still no luck guys please help. I've replaced fuel tank, sending unit, fuel pump on frame, oil pressure sender, new filter housing assembly with new heater. It cranks a few seconds before it will start and then it still won't take fuel for a while. I can crack the water drain valve, crank it over then close it and it will start right up and run good. I check the pressure today, my gauge doesn't read low pressure very well but it looked to be around 7-8psi while cranking and running, but when I shut truck off the pressure drops off pretty quick. It acts like it loosing it's prime. I have wired pump straight to power to check for fuel leaks and everything is dry. Please help me guys I'm lost and I want to get this truck on the road I have way too much money in it now to sell it.

When you say it runs good, does that mean you drive it for hours straight with no problems?

Yes drove it all day yesterday and runs great. I can even stop and turn it off and start it back immediately and it still won't take fuel for a few seconds. Once it starts taking fuel it will run normal

You are confusing me. You say the fuel pressure drops when you cut the truck off, as it should considering you cut power to the lift pump. I don't see how that is a symptom of anything.

With the water drain valve open and "cranking" doesn't make sense either. Any lift pump pressure will be weakened by having a bypassed line. I don't see how that will help fuel delivery, if anything make it worse.

You got a weird bug there, might be a loose/bad wire connection or a sock restriction would be my best guess. What brand of sending unit did you install?

I had a fuel pressure gauge hooked to the drain valve therefore I had to open it to get pressure to the gauge, I'm not sure how fast the system is suppose to lose pressure once it's shut down. Not sure on brand of sending unit but all my issues were happening before I started replacing parts so I know the parts I've replaced has nothing to do with the problem. I'm not familiar with these 6.5 fuel systems so I just been guessing with parts. It acts like it looses it's prime and has to build it back up before it will start to rev. All I know is when I start it I cannot just take off driving, it will start pretty good, it cranks a few seconds but it is a diesel then it will start and idle fine, but when I press pedal down it will not rev. After it runs for a few minutes it will start revving and running normal. It's like the injector pump is waiting for some type of info before it will let the accelerator work. I've checked all the wiring and everything I know to check. The only thing that makes a difference is if I open bleed valve on top of filter housing and crank it until fuel comes out then close it, the truck will almost immediately take of revving like it should. I'm lost and I can't afford a $1000 injector pump if it's not bad.

try plugging it in over night and start it up, rev it a couple times then drive it. report back.

I've tried plugging it in a few times, it doesn't make a difference, it still won't rev up. The temperature doesn't affect it, the glow plugs are working also

dumb question, have you put a pmd on it yet?

Nope just ordered one today with a relocation kit. I found a nice trick today though. Wrap your minds around this. I can start the truck and it will idle and not rev as usual. I can go out and give it a shot of starting fluid and make it rev up then it will take right off and start revving with the throttle. I done this 3 times so it's not coincidence.

tricks aside it seems like an electrical issue to me and here is a prayer for the pmd fixing it. if it doesnt its injection pump time.

Try swapping out the electronic throttle control thingy.

I replaced the accelerator pedal already if that's what your talking about.

swaptronix is the worst. :argh:

Pmd didn't help it. I'm so aggravated with this thing. I've spent a fortune in new parts and can't get any help. I've called stanadyne for support about 10 times and they won't even return my calls. It has something to do with the idle because I can give it a shot of juice a it'll take right off running great and idle where it's suppose to. Before the juice it'll start and idle but very low. The only thing I haven't changed is the pump itself but I just can't conclude how the pump would be bad since it'll run all day long great after I get it to take the throttle. It's like it doesn't even recognize the throttle action when the idle is below a certain rpm.??????

I don't understand why you would call standyne? I have also been avoiding it but you cant just keep blindly changing shit and getting upset that its costing you a ton of money. 6.5s are incredibly simple and 2 minutes with a scan tool would have bypassed allot of this. If their are no codes, fuel flows out of the fuel drain, and the pmd is good there is really only 1 option left. If it was me i would try advancing the injection pump, doing an optical bump, running a high quality system cleaner through it to try and salvage the injection pump. But please stop saying it wont take fuel it sounds like you are having trouble putting fuel in the tank.

Well let's see, stanadyne manufactures the ds4 injector pump that's on my truck and no one else will explain the technical order of the operation of that pump. And I haven't been blindly replacing parts, I have taken advice from these forums telling me I have a fuel restriction, bad lift pump, ops, or pmd. And I guess instead of won't take fuel I should say when I press the accelerator pedal with my foot the engine rpms won't rise to make the vehicle move in a forward or rearward motion. If a scanner would show an obvious problem I would have had it fixed 3 months ago.

standyne didnt sell it to you and they dont have a free tech line. If you had a scan tool you wouldnt have changed the throttle pedal. This forum advice has been to inspect for fuel restriction, lift pump, ops, not change them all. PMD, yea its a little box of 1000 mysteries you cant really check it and it does all kinds of funny stuff when they are bad. OR you could just say the engine wont rev until it warms up a bit and idles low. Like i said, if the pmd is good, no codes, it drives normal after it runs a bit, fuel comes out of the fuel filter when you crack it there isnt much left outside of the main injection pump. It could be wore out and has trouble pumping initially, could be retarded from warn timing chain, could be a ton of things. Just trying to get you on the right path here.

Thanks I'll try to bump timing up and see what happens. I'll try anything it's driving me crazy. Do you guys think it's a possibility someone has it addicted to starting fluid? I've always heard that phrase but never knew if it was possible?

Also would a video help understand my problem better? I didn't realize that my explanations were so misunderstood.

video wont hurt.

Have you done the 2000 rpm test?

with engine fully warmed up in park do a couple of quick accel/decels to 2500 rpm, 2-3 times, then slowly accelerate to 2000 rpm as best you can run-up in 100 rpm increments, to next 500 rpm and hold for about 30 sec, then go up another 500 rpm in 100 rpm increments and hold s Once you get to 2000 do same thing on way down back to idle, see if rpm is steady or is it hunting, since you have swapped APPs and PMDs I suspect you have a worn or wearing IP fuel distribution armature plunger .

Do you run any lubricity additives? Try adding 1 qt cheapest you can find SAE-30 non detergent engine oil I buy generic stuff at dollar general or whoever has best price , add 1 QT to a tank fill up thay may help for a while with "sticking plungers/armature that I suspect when cold are sticking a little and when warmed up the clearances of the worn parts are not as tight when cold.

How old is the IP?

Another thought how clean are your grounds, that go to the PCM the one that goes between firewall and block, and also the one on pass side aft intake stud by trans dipstick, have to be spotless, I clean them and keep dielectric grease on them for long term.

Remember these puter controlled trucks have sensors 0-5V, if dirty or loose grounds are present inputs for things like feedback loops to puter can be incorrect, more to the gnds (about 20 gnds for OBS GM trucks) on these trucks (all modern vehicles actually) than just the engine to battery gnds.

If you don't have a factory manual to see them a subscription to AllDataDIY I think $33/yr is invaluable renewal is less but you can print from AD-DIY site all your wiring diags and make your own manual Haynes manuals are junk for the 6.5TD trucks search ebay-amazon etc for a set of factory manuals, no longer in print from Helm Inc (OEM site).

I had to make two separate videos, the first time the truck made me a liar lol. I finally drove the trick enough to get the cel to come on. It's throwing a 35 and 36 code. I had it in diagnostic mode in video is why the lights are flashing.

Just finished a 100 mile drive and my final codes are 34,35,& 36. I noticed 34 is something to do with injection timing. How do I check it and how do I adjust it?

Checked everything discussed, hooked truck to scanner and everything looks good. The desired ip timing and actual are right on. Boost looks good, fuel pressure good, fuel temp good. Only flag is the coolant temp sensor shows 304℉ plugged in or unplugged. Doesn't make a difference on love data but when I unplug it the motor revs up. If I leave the coolant temp unplugged truck will start up and run normal. I have tried 3 different sensors including ac last time. I don't know why the ecm is showing 304℉ but if it's trying to compensate for that would probably cause my problem??? Still throwing 35 & 36 code also. But driving truck everyday now even though everything I'm doing is apparently wrong it's getting me back and forth for now.

Hmm. Could the high temp reading be putting the PCM in limp mode?

hello not to sure but i think these vehicles have two temp sensors....one goes to the gauge and one tells the putter what the ambient temp and tells the putter how much fuel it takes and how long the glow plugs stay on....i used to own a trucking company and yes the grounds are very important... since the putter and some of the sensors work on very low voltage....when i got a new teuck the first thing i did was check all the grounds and added several.... and i never had alternator issues or putter issues...i love the 6.5 if they are running right... and like the member said they are very easy to work on...... and the crank position sensor ,,,,,the plug in might look good but the sensor itself is down by the frt seal and below the oil fill.... and since it is an older truck the previous owners might have spilled oil down the frt of the engine....and oil deteriorates rubber ....and guess what the insulation is rubber... the crank position sensor also controls the timing IP....might want to check that also...