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Excessive Cranking to Start

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Ever since I've had the truck, it's only had to barely crank once to start the engine. Now it has to crank 10, 15 sometimes 20 times before it will start. It runs fine after starting. I have a two year old Blue Chip VP44, a new lift pump and good fuel pressure and have hand over handed the entire fuel system looking for leaks. This includes: injectors, supply lines, return lines, banjo-bolt o-ring seals, fuel line steel tubes to hose connections and have detected no leaks. I have no codes showing. A fellow Cummins owner thought it might be as simple as a faulty fuel cap not venting and drawing a negative pressure on the tank, causing the fuel to syphone back to the tank from the return line, loosing prime.Any ideas?Thanks.

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Just tried the fuel cap idea, no dice. Still cranked 10 times to start. Also, now there is a P0500 code: No Vehicle Speed Sensor Signal. I wouldn't think that this would be related to the cranking issue but.....? Should I replace the Speed Sensor? If so, where exactly on the transmission is it located? All the shop manual tells me is that it's located in the Overdrive Gear Case, over the Park Gear. I could use a pictoral of the location if there is one out there.

Thanks.

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What is your fuel pressure like?

Also did you do the lift pump diagnostics?

http://mopar.mopar1973man.com/cummins/2ndgen24v/lift-pump-diag/lift-pump-diag.htm

Bump the starter to activate the transfer pump. Look for air bubbles. If no air bubbles are present, proceed to step 10. If bubbles are present, check the lines/connectors between the fuel tank and the transfer pump for conditions allowing air to be drawn into the fuel system. Correct the condition and repeat steps 6, 8, and 9

Most of the fuel system is a vacuum line so leak never leak outwards but they sure suck inwards without leaving a wet spot...

Just tried the fuel cap idea, no dice. Still cranked 10 times to start. Also, now there is a P0500 code: No Vehicle Speed Sensor Signal. I wouldn't think that this would be related to the cranking issue but.....? Should I replace the Speed Sensor? If so, where exactly on the transmission is it located? All the shop manual tells me is that it's located in the Overdrive Gear Case, over the Park Gear. I could use a pictoral of the location if there is one out there.

Thanks.

Speed sensor is in the top of the rear diff... The P0500 error code explained here...

http://mopar.mopar1973man.com/cummins/2ndgen24v/abs/abs.htm

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