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99 GMC Yukon Denali 5.7 V8 - Intermittent long crank

by airpark124 on Jan 23 2018, 5:13 PM

This Denali will intermittently have a long crank. I have replaced the distributor rotor & cap, spark plugs & wires, fuel pressure regulator, fuel pump & relay, fuel filter, fuel lines, the cpf injector assembly, and though it has improved it still every now and then has the long crank. It doesnt seem to dependent of temperature because it has happened in hot & cold weather. I checked the coolant temp sensor & also the tps sensor and they show to be working properly even when the car is having the starting issue. I'm getting ready to change the crank sensor and cam sensor to see if that has anything to do with it. I added some sea foam and that helped a little as well.

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5 Replies

By jeffreyd1 Apr 09 2018, 8:57 PM

Long crank times w/no codes are generally fuel system related. I would suspect that the fuel pump is failing or the fuel pressure regulator is not holding. It looks like you have replaced the injector assembly & the fuel pump both. If you cap the fuel return line, you can tell if the fuel pressure is bleeding back off through the pump or through the regulator.

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By lorenz582 Apr 05 2018, 4:19 PM

have to put a scope on the crank sensor?

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By 1986chevyman Feb 09 2018, 8:53 PM

I would hook up a F/P guage and see if the fuel pressure is just taking a while to build up. The new fuel pump could be bad. The check valve in the fuel pump should at least hold some residual pressure in the lines so start up will be quick. Fuel pressure needs to be at least 55psi to start, preferably closer to 60 psi. Also did you check the F/P connector? Have seen some of these with poor connections making the F/P not perform optimally.

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By shadetreetech Jan 25 2018, 4:20 PM

Wow! These problems can be the most frustrating! My mind keeps going back to a fuel pressure loss; Such as a bad fuel pump check valve bleeding down. I know you put a new pump and sender in but new is new not necsisarly good. I think I would leave a fuel pressure gauge on it while you drive it through your daily routine. Just to be sure.... Keep us updated!

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By benelli7518 Jan 23 2018, 11:59 PM

i am not really sure what else it could be....my next step would be the same thing your doing

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