My 2003 Cummins H.O. is taking a while to start. The starter takes a little while to get the flywheel spinning at 200 RPMs, but once it hits 200 it starts right up. I am curious since my cummins has a larger flywheel and a tighter compression ratio (17.0:1) than the regular common rails; if my starter might not be the same as a typical common rail cummins? I am about to replace the lift pump just because I don't trust the stock one. The truck only has 140000 miles.

 

Do a voltage drop from b+ the starter while starting. Might also want to check starter current draw. Most likely faulty starter. Why are you replacing the lift pump, worst case scenario would be a no start or maybe a stall, and in alot of those cases low power issues or low rail pressure codes pop up first.

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Thanks... I will test out the starter and see if it just isn't up to specs. I ordered a new lift pump because I want to start my supporting modifications before I start modifying anything. Plus adding a good lift pump will take some of the pressure off the injector pump.

 

It won't create any problems for the injector pump. Most common rail cp3 engines don't even use a lift pump. If your going to mod though it'll have to be done sooner or later.
Do you understand what I mean by voltage drop test?

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No I don't know what you mean by voltage drop test. How much of a voltage drop should I see? When I start to crank my truck it drops from around 14 volts to around 9 then the flywheel finally starts to turn over fast enough. I have to plug the truck in overnight if the temp is going to below 40. I am also wondering if I could have a combined issue with my heater grid. I checked the voltage at the grid plate and its fine, so I pulled the grid plate itself and hooked it up to a car battery. The plate barely got hot, if I left my hand on it I would get burned eventually. I always thought those things were supposed to get red hot, kind of like an element on a stove.

 

Voltage drop test is where you take the negative lead of your meter, place it on the positive side of your battery then place the positive side of the component your trying to verify the wiring to, in this case the starter. The voltage shown is the difference in potential between the two points. In high amperage circuits most consider 1v of drop typical. Anything above 5v would likely indicate corrosion in the wire or damaged terminals. Grid heaters circuits can be tested the same way. Open system voltage (cables off) on the battery should be 12.60v anything lower indicates a weak battery , 11.70 or lower indicates the battery is completely discharged and should be recharged and retested.

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Thank you for the advice; it is much appreciated. I will try this on the starter. I did something similar with the power going to the grid heater. I have also checked the continuity of the circuit of the grid heater and it shows a short from the battery to the relays and a short from the relays to the grid heater which leads me to believe that the wiring isn't corroded or open anywhere. I also checked the continuity of the grid plate itself across both the heat fins and it reads as a short. Shouldn't the grid heater has some resistance across it so that it can heat up?

 

Continuity or resistance is pretty much worthless unless checking simply for connection or the condition of a set component. All of the items in question require loaded testing. For instance, while commanding the grid heaters on you'd check for voltage (or voltage drop) at the solenoid on the wire that runs from the battery to the solenoid, then at the grid heater where the wire connects. Once this is done you can address faulty components. Grid heaters are high amperage units and have a very low resistance and therefore generate lots of heat.

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ok. I'm taking the truck to my buddy's shop today and will check the starter and the grid plate circuit for a voltage drop. Hopefully I can make some headway today on this issue. I've already had to change the batteries once. I would hate to have to change the batteries again if this long crank time issue keeps up.

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OK. I tested the starter, alternator, and the batteries and they were all good. I used some Snap-on diagnostic thing that gave me a printout of the voltage drop and everything. I also hooked up this Snap-On Tester to my OBD-2 port and ran some function tests. After fiddling with all of my air intake heater connectors the function test was able to cycle on both of my heater elements. So there are two positive notes. The bad thing is that my truck still takes longer to crank than it should. I am installing my new lift pump tomorrow. A mechanic mentioned that I could have some gelled diesel stuck to the lift pump in my tank and that might be causing the problem. Seems unlikely, and I would have problems while the truck was running.

 

A: find a new shop.
B: there is no tool on the market that you can hook up and it show voltage drops except for a lab scope or dvom.
Fuel pressure and volume should be a one of the first test. How was the starter tested? Slow cranking speeds typically always lean towards starter or batteries.
If a starter is failing we of course have ways to confirm this but it's typically not done with a one tool does all type of battery tester. The ed18 is a pretty advanced system tester for battery, starting and charging systems. Actually probably the leading tool in the industry but it's still limited in starting system test. Also you mention that after messing with the wiring you were able to determine that you could make the grid heaters work. If they were not working and it was wiring related the voltage drop test would have show a very high voltage. Could you post a video on YouTube of what you consider slow starting?

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