My R50 has been giving me trouble cranking lately. Sporadically. When it does, it will almost crank, then start "cranking faster". Sometimes it will start, then immediately shut down. Outdoor temperature or humidity seems to have no effect. When it runs, it runs fine. No skipping, etc.

My question is, what do I most likely need to do?

Spark plugs? Fuel filter? (don't say fuel pump, please), other?

The fuel pump won't cause a slow crank, so I doubt that. Crank or cam sensors are among the "usual suspects" for a problem like that, as is the MAF. Any of those can cause crappy starting behavior without throwing codes.

VStar650CL wrote: ↑

Wed Jan 26, 2022 10:59 am

The fuel pump won't cause a slow crank, so I doubt that. Crank or cam sensors are among the "usual suspects" for a problem like that, as is the MAF. Any of those can cause crappy starting behavior without throwing codes.

I just replaced crank position sensor about a month ago with aftermarket one. I have since bought a genuine Nissan one to replace it (because it's a once a year thing). I haven't installed the Nissan one yet. I always thought that was basically a start/no-start thing.

Haven't thought about the MAF.

I can't tell you how much hair I've seen pulled out over the years because of crappy aftermarket CKP's and CMP's. So that aftermarket CKP would definitely be #1 on my suspect list. On an early VQ you'll get a long crank from a CKP that's flatlined or missing teeth, but not usually a no-start. Bad CMP's are different, you will get a no-start from those.

I am hoping I am doing this forum thing correctly. I have a slow crank issue after 2000 PF has been driven and sits (at least 20min). We have replaced the following upon mechanic recommendation. (Differnt shops because no one can seem to figure it out)
Dist. and cap, wires, spark plugs, realy, fuel filter, IAC valve, fuel pressure regulator, crank position sensor, cam shift sensor. (MAF a few years ago). Mechanic says it is probably the ECM. He cannot get any communication from the scan tool. It runs and drives great when it cranks. Thoughts?????
Hubby is getting tired of dealing with it but I love it and want to keep it if possible.
Thank you in advance.
Emily

Is this a "slow" crank or a "long" crank? I.e., is the starter spinning audibly slower than normal, or does the starter spin at normal speed but it spins-and-spins without starting? If it's the latter, the usual suspect on R50's is the Fuel Pressure Regulator. They leak internally and flood the engine after a brief hot-soak. It's a very common issue. However, with that being changed and a scan tool not connecting, do some voltage drop testing on your main grounds and power and ground to the ECM. That's especially true if it's a "slow" crank.

These may help:
keep-your-engine-on-the-ground-not-just ... 28130.html
https://www.nicoclub.com/archives/under ... tests.html

VStar650CL wrote: ↑

Mon Apr 18, 2022 4:27 pm

Is this a "slow" crank or a "long" crank? I.e., is the starter spinning audibly slower than normal, or does the starter spin at normal speed but it spins-and-spins without starting? If it's the latter, the usual suspect on R50's is the Fuel Pressure Regulator. They leak internally and flood the engine after a brief hot-soak. It's a very common issue. However, with that being changed and a scan tool not connecting, do some voltage drop testing on your main grounds and power and ground to the ECM. That's especially true if it's a "slow" crank.

I
Thank you so much for both replysand so quickly. If I drive it for the next month will I do significant damage? I am not having to start it except for the work day really. I am going to have the mechanic do the testing. That is all greek to me! (I have only ever had the service engine light come on once and that was the MAF.) Thanks again!

VStar650CL wrote: ↑

Mon Apr 18, 2022 4:27 pm

Is this a "slow" crank or a "long" crank? I.e., is the starter spinning audibly slower than normal, or does the starter spin at normal speed but it spins-and-spins without starting? If it's the latter, the usual suspect on R50's is the Fuel Pressure Regulator. They leak internally and flood the engine after a brief hot-soak. It's a very common issue. However, with that being changed and a scan tool not connecting, do some voltage drop testing on your main grounds and power and ground to the ECM. That's especially true if it's a "slow" crank.

Sorry I didn't answer your question. It sounds the same to me just takes a long time before it starts. If tried right away a second or third time then it takes even longer to start.
If it's been hours in-between starts it starts just fine.
Thank you again.

That's odd, the usual causes for that are the Fuel Pressure Regulator and the Cam Sensor (in the distributor), but you've already changed both. It won't be the Crank Sensor, VG33's only use those for diagnostics and they won't cause starting issues like VQ35's. I think the main clue is the scanner not connecting, track down why that's occurring and you'll probably get to the bottom of things. Don't know which relays have been changed, but the ECCS Relay (in the under-hood Fuse & Relay Box) would have to be considered a candidate, as would the Ignition Switch. You might want to print out EC-137 and EC-138 here for your mechanic if he isn't a Nissan dealer or specialist, not everyone will have access to old Pathy documentation:
https://www.nicoclub.com/service-manual ... 0%2Fec.pdf
Of course you can also direct him to Nico for the full FSM.

Thanks a bunch.

Now I am having the same issue as we3tjs... Cranks up fine first thing in the morning. But once warm, it struggles to crank. Takes 2-4 tries every time (starter turns over normally). I did replace Crank P.S. with OEM last year.

The late R50's with the VQ35 are a completely different animal from @we3tjs's VG33. Almost nothing in this thread applies to your engine. Try cam sensors, those would be the next most likely culprits on a VQ.

VStar650CL wrote: ↑

Tue Feb 21, 2023 9:35 am

The late R50's with the VQ35 are a completely different animal from @we3tjs's VG33. Almost nothing in this thread applies to your engine. Try cam sensors, those would be the next most likely culprits on a VQ.

Isn't one easy to get to, and one pretty difficult to get to?

Yep.

Did you guy's get your long crank problem fixed? I had what seems like the same issue- started fine if cold but warmed up it would take a couple long cranks to get it to fire up. For me, it was the fuel "damper" at the right/front of the engine, not the FPR. At the picky pull they just gave it to me, free fix.

Thanks so much. I will try that! We have a couple u pull it yards I can go to.