7.4 mpi hard start when cold

zaverin1

my friends boat has developed an issue during cold starts.

if the throttle lever is slightly cracked open it fires right up and runs great.
When he fires up the boat with throttle lever in idle position it just crancks and dosent start.
huffs and puffs.

i Told him that it might be iac or tps.
He lives on the west side of the state so I can’t just go there to diagnose.

thoughts
when throttle Is cracked on a mpi engine and it starts it usually ends up being iac or iac filter but I did see some tps sensor cause the same issue.

Black_Diamond

I’d start with the IAC, but a bad IAC would not let it idle at all usually.  Where’s he located in West Mich?

zaverin1

Cottage by silver lake 
it’s a trailer boat 

Stodge

If it had carbs I'd say that was normal.  Maybe a fuel pump is getting tired and not pushing enough fuel at idle but more when the throttle is advanced?

zaverin1

Once warmed up it runs and starts fine 

zaverin1

I would bring my laptop and plug in but don’t feel like driving for 3 hours 

zaverin1

Fuel  pump pushes same psi regardless of throttle position Stodge 

212rowboat

zaverin1 said:

Fuel  pump pushes same psi regardless of throttle position Stodge 

i think he was saying "if it were carb'd" as in "if it was also a mechanical FP"... 

check the throttle linkage for slop or bind first.  if the IAC is mapped almost closed because the throttle plate is opened slightly due to bind or slop, it will manifest almost precisely like a bad IAC.  and another thing- if this actually is the issue, it will take the ECM a little bit to remap and account for the new TPS and IAC settings.   

zaverin1

Ye
he thought it was fuel pressure regulator and I told him if it runs great at full throttle and idles great once warmed up it’s not the culprit.
early 7.4 mpi didn’t have a iac filter new ones do.
i will tell him to clean the throttle body
adjust or check the linkage.
then get iac and tps 

zaverin1

Yes sir 
awesome area
he ended up cleaning his fire arestor and change out the iac 
problem solved
i usually go to his cottage there twice a year
once in the summer and once in the winter 

we use to sled together but after my motorcycle accident I gave that up. Not because I am scared lol because my back can’t take it 

zaverin1

Nice