Archived hard hot start

[KCohen]

I have a '99 1 ton,5 speed that threw a code fo the TPS about 3 weeks ago. Now I have a hard time starting it after ive been running it. If it sits overnight it starts fine,but try to start it after going out to eat some where you'll almost where down a battery trying to get it started. I replaced the TPS sensor assembly($390. 00) and the lift pump($185. 00) and still have same problem. Truck still runs good but poor fuel milage(14 mpg). Help!!! thanks,Kelly

 

[tp0d]

Kelly,



First, Welcome to the TDR.



Well, having not worked too much on 24v's I can point you in the direction of a couple things...



First, take out the MAP sensor (I think its in the intake manifold, but I could be wrong) and clean it up real good with some carb cleaner/wd40/etc. then reinstall.



Second thing to try, unplug the temp sensor in the block, drivers side towards the rear . Its a two wire jobbie... Theres been issues with the sensor failing hot and the ECM says 'no way'



third, and just a generic, check all wiring points for any looseness or corrosion, and unplug and replug if possible. I would also recommend unplugging, cleaning with contact cleaner, and replugging the ECM plugs. Bad grounds are the most common failure.



the map sensor could be the cause of the fuel mileage also. . Sorry I cant be of more help, just havent worked on the 24v's that much. .



good luck



-j

 

[KCohen]

Thanks tpOd, I'll try them and let you know how it turns out.

 

[JR2]

How old are the batteries?? Maybe they are just not up to the task when they are warm?



After that it sounds like you might need to look into this TSB:

http://dodgeram.info/tsb/2000/18-15-00.htm

 

[2-ND TIME]

With it hard to start when it is warm leads me to think that it is pulling air in the fuel system. after the lift pump? Because it can't dispell the air and it can't compress it? So try to bleed at the top of the fuel filter bump the starter and open the ??? 1/8" pipe plug at the top. Crack number ??? 1,3,4 fuel lines and let the air out. It will run rough for 3 or 4 minutes so not to worry mine will run with 1 cylinder pumping fuel all over me. ( big grin grr). Will need a 17 mm spanner. Open #1 a lot and crack the other 2. You could have a leak at the banjo fitting on the side of the vp-44 is there signs of extra wear? the ?? o-rings or gaskets are available at cummins. maybe the pressure relief valve could be the leaking culpit? Don't run the starter as long as you have been. not good for it. Hope this helps.

 

[KCohen]

thanks all for feed back. batteries in truck are good and havent had chance to work on it yet. i'll try bleeding lines and see what happens after checking all the map sensor,etc. Just glad I still have my faithful '91 cummins to keep me on the road. Thanks again,Kelly

 

[rkressg]

Check the T-Fitting on the fuel return line. It is back behind the fuel filter housing, above the lift pump. If disturbed, it can leak (compression fittings), allowing air to be introduced into the fuel system causing a hard start problem. Also, you can check out that TSB for the hard start reflash, but if I remember correctly, that was only for automatic trucks.



I hate to say, but a hard start when hot is a classic symptom of a failing VP44. What are your fuel pressures during cranking? Having more than 3psi of fuel pressure during cranking to the feed side of the VP44 can cause a hard start condition, especially on the older pumps. Check this with a mechanical FP gauge. Hope this helps.

-Rich

 

[KCohen]

Thanks Rich. That vp44 has been my biggest fear but I dont understand why the truck runs good and starts so readily in the morning but I do understand that when pumps get hot and are worn they start giving us problems. I guess Im in denial and dont want to spend the big bucks Yet. Thanks again,Kelly

 

[justinp20012500]

Hard starts can be a number of things.



Check to make sure you are not leaking an excessive amount of fuel out the return located at the back of the head.



Injectors that have high mileage on them can be popping too low and cause a bleed in the system.



The connector tubes that connect the injector to the high pressure lines might be leaking, but you would not see the fuel out side of the head. It would leak in the head and return to the tank via the banjo botl/return line on the back of the head.





Justin