7.4 Mag IAC/Fuel Pres Reg Replacement Intake Removal?
04-22-2019, 01:05 PM
#1
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7.4 Mag IAC/Fuel Pres Reg Replacement Intake Removal?
Need to replace the IAC and fuel pressure regulator on one of my 7.4 Mag motors. Never worked on these before. Do I have to remove the big "bread box" intakes off to get to everything? Do I pull the torx button head bolts out and then pull it off? Seems like the only way to get to anything. Will I need to replace plenum gaskets? Can't find anything about it on YouTube.
Thanks.
Thanks.
Last edited by BajaFresh; 04-22-2019 at 01:11 PM.
04-22-2019, 11:27 PM
#2
You might be able to access the IAC easier with the flame arrestor removed but it can still be difficult. Pulling the top half of the intake off makes it significantly easier. Yes the torx button head bolts need to come out. There is a very thin gasket between the top and bottom half and I don't believe it is available anymore. Proceed with caution in that regard. If the gasket is not damaged it can be reused.
Don't drop any items down the runners with the top removed! Ask me how I know! lol I had one of those button head bolts drop down runner. It was virtually out of sight and since it is stainless I couldn't fish it out with a magnet. Took some creative McGuyvering to retrieve. Basically a wood dowel with a wad of sticking tape on the end.
Don't drop any items down the runners with the top removed! Ask me how I know! lol I had one of those button head bolts drop down runner. It was virtually out of sight and since it is stainless I couldn't fish it out with a magnet. Took some creative McGuyvering to retrieve. Basically a wood dowel with a wad of sticking tape on the end.
04-23-2019, 12:00 AM
#3
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Thread Starter
You might be able to access the IAC easier with the flame arrestor removed but it can still be difficult. Pulling the top half of the intake off makes it significantly easier. Yes the torx button head bolts need to come out. There is a very thin gasket between the top and bottom half and I don't believe it is available anymore. Proceed with caution in that regard. If the gasket is not damaged it can be reused.
Don't drop any items down the runners with the top removed! Ask me how I know! lol I had one of those button head bolts drop down runner. It was virtually out of sight and since it is stainless I couldn't fish it out with a magnet. Took some creative McGuyvering to retrieve. Basically a wood dowel with a wad of sticking tape on the end.
Don't drop any items down the runners with the top removed! Ask me how I know! lol I had one of those button head bolts drop down runner. It was virtually out of sight and since it is stainless I couldn't fish it out with a magnet. Took some creative McGuyvering to retrieve. Basically a wood dowel with a wad of sticking tape on the end.
04-23-2019, 08:00 AM
#4
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Gaskets are still available for the upper plenum. You will likely need them as the little buggers with the print-o-seal on them do tend to stick and are delicate. Extremely overpriced at $39, but it is Merc and not used on anything elsewhere in auto world.
https://www.cpperformance.com/p-4795...-805522a1.aspx
With that vortech billet arrestor, you should remove the 4 stainless allen heads holding that on and the throttle body will come right off. IAC is mounted underneath and is a 5 min swap even with pulling arrestor off. there is a gasket between the TB and plenum though, I've never had one rip and stick however and have been able to reuse. No need to remove the upper plenum just to change IAC.
You will likely need to remove upper plenum to change fuel pressure regulator as it is mounted on the back of the fuel rail.
Why do you need a new IAC? Do you have a known fuel pressure issue? If your fuel pressure is low, the new regulator will likely fix the poor idle issue if that is what is happening.
https://www.cpperformance.com/p-4795...-805522a1.aspx
With that vortech billet arrestor, you should remove the 4 stainless allen heads holding that on and the throttle body will come right off. IAC is mounted underneath and is a 5 min swap even with pulling arrestor off. there is a gasket between the TB and plenum though, I've never had one rip and stick however and have been able to reuse. No need to remove the upper plenum just to change IAC.
You will likely need to remove upper plenum to change fuel pressure regulator as it is mounted on the back of the fuel rail.
Why do you need a new IAC? Do you have a known fuel pressure issue? If your fuel pressure is low, the new regulator will likely fix the poor idle issue if that is what is happening.
Last edited by Gimme Fuel; 04-23-2019 at 08:06 AM.
04-23-2019, 09:01 AM
#5
Registered
Thread Starter
Gaskets are still available for the upper plenum. You will likely need them as the little buggers with the print-o-seal on them do tend to stick and are delicate. Extremely overpriced at $39, but it is Merc and not used on anything elsewhere in auto world.
https://www.cpperformance.com/p-4795...-805522a1.aspx
With that vortech billet arrestor, you should remove the 4 stainless allen heads holding that on and the throttle body will come right off. IAC is mounted underneath and is a 5 min swap even with pulling arrestor off. there is a gasket between the TB and plenum though, I've never had one rip and stick however and have been able to reuse. No need to remove the upper plenum just to change IAC.
You will likely need to remove upper plenum to change fuel pressure regulator as it is mounted on the back of the fuel rail.
Why do you need a new IAC? Do you have a known fuel pressure issue? If your fuel pressure is low, the new regulator will likely fix the poor idle issue if that is what is happening.
https://www.cpperformance.com/p-4795...-805522a1.aspx
With that vortech billet arrestor, you should remove the 4 stainless allen heads holding that on and the throttle body will come right off. IAC is mounted underneath and is a 5 min swap even with pulling arrestor off. there is a gasket between the TB and plenum though, I've never had one rip and stick however and have been able to reuse. No need to remove the upper plenum just to change IAC.
You will likely need to remove upper plenum to change fuel pressure regulator as it is mounted on the back of the fuel rail.
Why do you need a new IAC? Do you have a known fuel pressure issue? If your fuel pressure is low, the new regulator will likely fix the poor idle issue if that is what is happening.
04-23-2019, 09:38 AM
#6
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If fuel pressure is low, I bet the IAC is just fine. Chased same issue on my cool fuel MPI's. IAC did nothing, was all fuel pressure related. Issue solved when installed new regulators. Had hard start/wouldn't idle or would surge badly.
04-23-2019, 09:45 AM
#7
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The IAC is mounted to rear of throttle body. therefore just throttle body needs removing for this.
If this 502MPI is VST then regulator is on front of fuel rail. If cool fuel, the regulator is mounted don on the cool fuel module.
The upper intake gaskets and throttle body gaskets are still available:
https://www.mercruiserparts.com/bam/...31902/1614/180
Believe it or not,and not talked about much here,flepro offers these as a set and usually under $20:
If this 502MPI is VST then regulator is on front of fuel rail. If cool fuel, the regulator is mounted don on the cool fuel module.
The upper intake gaskets and throttle body gaskets are still available:
https://www.mercruiserparts.com/bam/...31902/1614/180
Believe it or not,and not talked about much here,flepro offers these as a set and usually under $20:
Fel-Pro 17852 Upper Intake/Plenum Gasket Set
04-23-2019, 09:52 AM
#8
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iTrader: (6)
11.99 @ Summit https://www.summitracing.com/parts/fel-17852
Edit : Id throw all that cool fuel VST chit in the trash, nothing but problems...
Edit : Id throw all that cool fuel VST chit in the trash, nothing but problems...
04-23-2019, 02:55 PM
#9
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Thread Starter
Okay, swapped out the IAC (easy) and fuel pressure regulator (kind of a pain). Had to pull the intake plenum off to get to the pressure reg mount bolts. Actually in ind site, I may have been able to replace it without pulling the plenum if I had known that the bolts were 5/16 heads but would have been a bit tricky.
Anyway, one of the gaskets ripped but the other three were okay. Of course no one has them in stock and I'm headed to Desert Storm on Thursday morning so just going to use form a gasket for now. I'm thinking there isn't a lot of pressure on the gaskets so it should hold for the weekend.
Anyway, one of the gaskets ripped but the other three were okay. Of course no one has them in stock and I'm headed to Desert Storm on Thursday morning so just going to use form a gasket for now. I'm thinking there isn't a lot of pressure on the gaskets so it should hold for the weekend.
04-23-2019, 03:18 PM
#10
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What is the new fuel psi ?
