unusual and intermittent "long crank" before engine runs

[Black06ram]

This happens once in a while, but its happened enough over the past two years that I would love to fix it. Truck is a daily drier 2005 dodge ram 1500 quad cab 2wheel drive 5.7L hemi with only 56,000 miles on it.

every few weeks it will take an extra 5 seconds of cranking to fire the engine. this has happened when the engine is cold and hasn't been used for days, yet also will happen minutes after I have turned off the engine after a lengthy drive. happens in all sorts of weather/temperature conditions also. when I say intermittent and random, that is the truth.

I am certainly mechanically inclined, so this has been confusing. its not a charging problem, its not anything that generates a trouble code either. this just happens maybe 1 time out of 30 times; the engine takes a while to kick over. typically the engine fires in 1-2 seconds, but when it has to crank for 5-7 seconds that gets annoying and odd. Have done research on here, on other dodge forums, etc. I can check the fuel pressure bleed-off with a fuel pressure gauge, but i really don't think that if it was fuel pressure related it would happen so infrequently. cam/crank sensor slightly off? wouldn't that cause general improper running, not just intermittent long crank?

thoughts ideas?

thanks!

 

[Black06ram]

yikes, nobody has any ideas for me to investigate??

 

[kevkev]

Fuel pump, perhaps? Just not bad enough to go bad?

 

[JohnnyMac]

yikes, nobody has any ideas for me to investigate??

When you shut the truck off, it should hold the fuel pressure in the system. If your fuel pressure check valve is sticky, the fuel system will lose pressure when the fuel pump isn't pumping so when you first crank it, it will take a few seconds for the fuel pump the charge the system up enough for the injectors to fire. My 2000 5.9 gasser did this, except it did it all the time. I had to just turn the key on and let the fuel pump charge the system before I cranked it. Not sure if this is the problem, but it's an idea.....

 

[Black06ram]

I was thinking it would be fuel system related or electrical/ignition related.

it is odd though. its so intermittent and unpredictable. I mean the truck can sit for a few days at times (and the pressure would bleed down of course during this) but it will usually start up fine. sometimes after running multiple errands with many hot on/off/on/off events it will all of a sudden do it. typically I will just hold the key cranking, and in a few seconds, the engine will fire. it wont display codes and i have even checked with my diablo intune tuner/reader. nothing, I know the pump and filter and regulator is in the fuel tank and under the truck bed, so its not a quick thing to examine; but I am trying to keep this truck reliable and dependable so I am hoping to figure this out before getting stranded someplace.

thanks for the advice fellas, feel free to keep it coming!!

 

[bigdodge]

Had a similar issue when the battery was getting weak. Tested fine but after replacing it stopped. I would set up a fuel pressure gauge that you can check before cranking

Sent from my Pixel 4 XL using Tapatalk

 

[Black06ram]

yea, that is an option. I have a fuel pressure analog/dial gauge I have used for other vehicles I own, so I could see if the fitting will connect to the ram 5.7. It would become annoying to pop the hood every single time I am going to drive the vehicle to check fuel pressure, but it might be something I can do. thanks

 

[10 Break]

So much on these trucks, especially our older ones, can be traced to ground/wire problems. If this were me, I'd inspect the crank sensor wires...look for an intermittent short

 

[Black06ram]

thats not a bad idea. right, if the crank signal isn't getting to the ecm, it wont fire the coils basically? I will certainly check this too, indeed, thank you. but also, wouldn't this cause intermittent misfires and drive-ability issues.. that I would certainly notice while driving?

I plan on checking any and all suggestions. so keep em coming fellas

 

[Bheezy27403]

Funny this came up. Mine did this today for the first time. '08 5.7 126k. I was turning the ignition on and off checking the lighting on my camper and when I went to start it it took a little extra time to turn over.

 

[atlas750]

My 2005 started doing the same thing, after about a month it is doing it anytime the truck sits for more than a few hours. The only way I get it to fire is by stepping on the gas and cranking it at the same time. Once started it runs great. In the shop for this problem right now.

 

[atlas750]

Got my truck back. Leaking #6 injector. Was replaced and now it starts easily!

 

[Black06ram]

ah! very interesting!! an injector leak, hmmm, I will keep that in mind when I keep troubleshooting my situation. glad you got your truck back and repaired!!


so far, since I typed this thread up two weeks ago, the truck has yet to do it! but I know its coming. like I said, its intermittent and random. I only drive the truck about 4 days a week. but yea, I will keep troubleshooting it and diagnosing it

 

[Black06ram]

so, truck has still yet to do it, but I am sure its due


did a fuel pressure check just because I had a moment. it primes to about 58 psi and then drops down if the engine isn't cranked. if engine is cranked it holds at about 58=60 psi. after key is shut off, it drops from 60 down to about 20 psi in about 10 seconds. then takes about a minute to drop from 20psi to 10psi, and then takes about 3 minutes to drop from 10 psi down to almost 0 psi. this seems entirely normal, but just figured i would let you know i did it.

i dont feel like driving around with a feel pressure gauge taped to the windshield for days/weeks (maybe months) until it happens again.

 

[WhiteExpress]

Not that it incredibly helps, but my '16 Ram does the same / very similar thing.
When we had it hooked up to a SnapOn brick the issue seemed to be in between the ECM and TB or the ECM itself.

Learned a few more things along the way:

The ECM has its default 'actions' it requests from the TB on start-up.
If you give it differing input (IE touch the gas pedal) your input overrides the default.

I've found that if I get in the truck, key on, cycle the throttle pedal, then start it, my issue seems to go away.

My shop swapped TBs with another truck for a week, it did NOT resolve the issue.

I don't believe they looked at injectors, interesting idea. Otherwise, the truck seems to run / drive pretty good.

 

[BEAST19]

Fuel issue, too much ethanol in our fuel now a days , allows for more moisture over time to build up. A tech at a dealership said this to me and I figured it was a bunch of ******** ..... he told me to run one or two tanks of non ethanol . Sure as hell.... within a week my problem was non existent. . I normally ran 93octane prior to this ... and when I switch back to the 93 octane (which has ethanol) for an extended period of time.... the symptoms of extended crank rears it’s head again...... hope this helps. Btw my truck is a 2015 ram 1500 with 34kmi


Sent from my iPhone using Tapatalk

 

[Black06ram]

hmm, very glad to hear everyone input on this odd/intermittent issue. these are all good possibilities. I am glad to have input from the forum on this topic! I wish I had some type of data-logger on this truck to record exactly what the engine/sensors are going through during the intermittent long crank. I have a data-logger on my camaro holley ****** and it is super helpful with troubleshooting issues. When I had to start diagnosing this long-crank problem with the ram, I felt like an old fossil cave-man as I am screwing on the fuel pressure gauge (ha, I a only 36 years old too). anyways. I will keep all the suggestions in mind as time goes on. !

 

[WhiteExpress]

I'm pretty tempted to grab a fuel pressure gauge and see if it's holding pressure. I'm sure there is an acceptable amount of bleed off back through the pump, but I imagine if I had a leaking injector it would drop off quicker.

 

[Black06ram]

yep, I agree. I only have my truck to test it on, so unless I have other people with previous knowledge or experience, I am kinda just stuck knowing what my "bleed down" rate is at.

 

[Dan98]

Had a 96 5.2 doing the same thing it was dirty injectors leaking down losing pressure. Cycling the key a couple times letting the fuel pump refill the system helps a lot

Sent from my SM-J260A using Tapatalk