Hard starts and weird tach

[Nathan Croxton]

As of lately my truck has become hard to start. It requires about two ten second cranks to fire but then runs great. I have checked for fuel leaks and tightness of fuel components. I installed a lift pump and new lines 9 months ago.  Also the tach doesn't match the speed you are driving. At light acceleration the rpms will jump all the way to 2k and on the highway at 60 mph it usually stays around 2700 rpm. I am not sure if it would be the crank sensor since I have no codes. The hard starting just happened out of the blue a couple weeks ago. Any help would great.

[Hawkez]

The hard start sure sounds like you are losing  your prime.  How long does your truck have to sit to create the hard start?  I have had to chase down a fuel leak before and it doesn't have to be a big leak.  Even the slightest leak can be a culprit if it sits long enough.

[CUMMINSDIESELPWR]

park nose downhill and see if it repeats. if it doesnt you have a air leak draining the fuel lines. might be time for crossover tube orings (installed dry)

[mopartechnician]

Connector tubr o-rings will only cause hard starts when engine is cold. I also install with bearing grease. You dont want to catch one

I would fix your tach issue first. I do believe the rpms is read off of cam and that is also what telks the ecm that the engine is turning over

[CUMMINSDIESELPWR]

i keep hearing both sides, dry/lubed... i guess to each their own :/

[CTcummins24V]

Connector tubr o-rings will only cause hard starts when engine is cold. I also install with bearing grease. You dont want to catch one

I would fix your tach issue first. I do believe the rpms is read off of cam and that is also what telks the ecm that the engine is turning over

 

Grease on the connector tube o-rings? Better than oil, seal it better?  

[mopartechnician]

You can use oil. I was just taught to use grease on all the fuel o-rings. It wont seal any better but I have never messed an o-ring up this way

Edited November 7, 2014 by mopartechnician

[Nathan Croxton]

If i park at home it can sit for days and start just fine. I noticed when i started parking in the shop at work. It would sit for 9-10 hours and be hard to start with a puff of white smoke coming out once it fired. the driveway at my house is barely at an angle. It does face downhill but very slightly. I thought i was having a fuel prime loss issue I just wasn't sure if the tach and hard starts were realted. There is no miss or loss of power that I have noticed. I'm starting to run out of things to replace, in the last six months I have done the IP, APPS , alternator, brake switch, speed sensor, and batteries. It never seems to end .

[mopartechnician]

Try leaving your fuel fill cap loose and see if the hard starts go away. Ive seen it before and i know its weird

[Nathan Croxton]

If the cross tube o- rings wouldn't it be damp around them?

[mopartechnician]

Nope, you have to remember that an air molucle is so small that it cant be measured. So you can have an air leak but not leak fuel.

[Nathan Croxton]

That makes sense. I guess I'll go ahead and do some o-rings. Any idea on where to get them? I looked on XDP and Geno's, they only have them for the common rails. Also any ideas on the tach issue? or how to find out what is causing it? 

[mopartechnician]

Cummins is the cheapest but I honestly think it wont fix it from the symptoms you have.

I would start first by wiring the fuel pump to the wiper fuse. That has fixed hard starts. Also I would throw a crankshaft sensor at it. I need to look to make sure that is what the tach reads

[Nathan Croxton]

my lift pump came with a wiring harness that hooked to the factory one. It was the quick connect one. I cant hear it cycle when i turn the key on and when it doesn't start you can hear it run as well as when the truck is running you can hear the pump run. I don't have a fuel pressure guage. I just didn't want to guess and start throwing parts at it. I know a crank sensor is around $50 which isn't terrible

[mopartechnician]

Cut the red wire between the relay and engine harness.

Splice a length of the same gauge wire to the red wire coming out of the relay.

Relocate this wire to a fuse that is hot only in the 'RUN' position. An example is the power window or windshield Wiper Fuse.This will cut power to the FASS or HPFP when cranking.

Edited November 8, 2014 by mopartechnician

[mopartechnician]

There is a trick that fass uses where you take the positive of the signal wire (out of the quick disconnect harness) and put it to the wiper fuses. The thinking is the lift pump will shut off durning cranking. I know its weird but I have fixed a couple hard starts this way. Its easy to test and to put back if it doesnt work.

[eddielee]

Replace your Crank sensor for the RPM issues. our year models use the crank sensor and newer ones use the cam sensor.

Remember to turn the sensor back and forth, breaking the seal, before removing so it doesn't stick and break.

Geno's sells OEM sensors

Edited November 13, 2014 by eddielee

[Nathan Croxton]

My crank sensor just came in today. I am going to do it on Saturday. I guess I'll try to figure out if I am losing fuel prime as well. I might put new crossover tube o- rings on just to be safe. I have heard about return lines on the back of the block causing loss of prime. I have never looked for them. Are they hard to get to?

[TFaoro]

They are a PITA ... but yes there is a banjo fitting on the back of the head with crush washers. It is a good idea to remove the fitting and replace the washers. Also check the T fitting where the head return connects to the VP return. 

[Mopar1973Man]

Lets say the fitting at the back of the head can be reach much easier with the valve cover off. I've got big hands so that extra bit of room really does count. Number 6 cross over tube is also in a tough spot too. If you pull the hoist ring off you can get #6 in and out much easier.