'03 5.0 MPI cranks but....

[fastexas]

My 200 sundeck with the 5.0 MPI A1 cranks and cranks and SOMETIMES starts (if can get it to cough to life then jam it into reverse to rev it). Just started happening this weekend. Once started in this manner it ran and idled fine the rest of the day. Re-started from warm just fine. Sunday morning would NOT turn over. Just cranked and sputtered a bit then the battery ran down trying to start it. Strong cranking while the battery lasted. Will be calling a mechanic later this week Any ideas what my problem might be??
182 hours if that means anything. Manifolds and risers replaced in May.

 

[Bay B's]

Cap and rotor ever replaced?

My 200 sundeck with the 5.0 MPI A1 cranks and cranks and SOMETIMES starts (if can get it to cough to life then jam it into reverse to rev it). Just started happening this weekend. Once started in this manner it ran and idled fine the rest of the day. Re-started from warm just fine. Sunday morning would NOT turn over. Just cranked and sputtered a bit then the battery ran down trying to start it. Strong cranking while the battery lasted. Will be calling a mechanic later this week Any ideas what my problem might be??
182 hours if that means anything. Manifolds and risers replaced in May.

 

[fastexas]

Not that I'm aware......but it would run well after starting and warm with bad rotor and cap?

 

[Bay B's]

My 5.0's would sometimes be very difficult to start, spit and sputter, and run like crap for a few minutes. Then I could get them to run OK. Seemed to be happening more and more often. Replaced cap, rotors and plugs in my case as the original plugs had ~350 hours and 9 years on them. Have been starting and running great since that work was done.

 

[jason78]

My 5.0's would sometimes be very difficult to start, spit and sputter, and run like crap for a few minutes. Then I could get them to run OK. Seemed to be happening more and more often. Replaced cap, rotors and plugs in my case as the original plugs had ~350 hours and 9 years on them. Have been starting and running great since that work was done.

This is great advice. What you have described sounds like time for a tune up.

 

[fastexas]

This is great advice. What you have described sounds like time for a tune up.

I it just a swap of the parts? Being an EFI motor are there any timing adjustments?.

 

[jason78]

No timing adjustments to change cap and rotor. Just remove cap, replace rotor, replace cap and put spark plug cables back on. Make sure to label the plug cables 1-8+Coil.

 

[fastexas]

No timing adjustments to change cap and rotor. Just remove cap, replace rotor, replace cap and put spark plug cables back on. Make sure to label the plug cables 1-8+Coil.

jason...is a bad ECM worth considering?

 

[tmo_7]

jason...is a bad ECM worth considering?

Please read my posts from 2014 on this subject. My motor is 5.0 EFI, 300 hrs. I believe I had the same symptoms you are experiencing. Merc insisted on replacing the ECM fo ~$4k. Another mechanic found root cause was faulty ignition coil. Mine had no issues with rotor, cap, plugs, or fuel.
from my research and speaking to specialists, is very rare to have a "bad" ECM.

http://clubsearay.com/showthread.ph...sed-as-Bad-ECM?p=774802&highlight=#post774802

 

[jason78]

jason...is a bad ECM worth considering?

I would say no at this point. I would start with basic tune up/preventative maintenance items as discussed such as plugs, wires, cap and rotor since you don't know the last time, or if they have ever been done. At the age of the engine, at least the cap, rotor, amd probably cables should be done regardless. The plugs might be OK with the low hours but I would just change it all. I have seen a corroded cap and rotor cause these same issues you have and they just appeared out of no where. I think it is less likely to be a problem with the ECM but anything is possible. Again, start with the basics that should be done anyway and work your way up.

 

[fastexas]

I would say no at this point. I would start with basic tune up/preventative maintenance items as discussed such as plugs, wires, cap and rotor since you don't know the last time, or if they have ever been done. At the age of the engine, at least the cap, rotor, amd probably cables should be done regardless. The plugs might be OK with the low hours but I would just change it all. I have seen a corroded cap and rotor cause these same issues you have and they just appeared out of no where. I think it is less likely to be a problem with the ECM but anything is possible. Again, start with the basics that should be done anyway and work your way up.

Many thanks Jason, for your advice and direction.....I'll post a follow-up after I do the work this weekend

 

[jason78]

Many thanks Jason, for your advice and direction.....I'll post a follow-up after I do the work this weekend

No problem, good luck! If those things do not help, I would look next at the ignition coil, as another poster suggested. You won't be loosing out though because the other things are PM that is due anyway.

 

[fastexas]

Success! Replaced cap and rotor on Saturday. Bought spark plugs but could NOT reach beneath the manifolds with the tight side clearances on the 200SD. Never the less, the cap + rotor replacement made all the difference. Started right up on first crank and purred like a happy kitten all weekend. Thanks to all for the advice. Now if I could figure out how to change the plugs.......