MPS inner adjustment screw, How do you get to it Options

[Dredwin]

Is this screw just the cover? I’m trying to get to the inner screw but I can’t unscrew the top screw. Sorry if the link doesn’t work.

https://www.amazon.com/photos/groups/share/...KNZsr2Q1omZTg2j

[Montreal914]

Paul Anders has great documentation of the D-Jet system.

This is the part about the MPS:

https://members.rennlist.com/pbanders/manif...sure_sensor.htm

[Dredwin]

Paul Anders has great documentation of the D-Jet system.

This is the part about the MPS:

https://members.rennlist.com/pbanders/manif...sure_sensor.htm

I saw that but can’t access the inner screw because I think of this cover. I know I shouldn’t mess with it without a special meter but my wife is dying to go for a ride and it won’t restart due to heat sink.

I just want to be sure I’m not breaking it if I muscle this screw off

[JeffBowlsby]

The way to get that outer stop off is to use a heat gun to remove all traces of the epoxy, then more heat while you gently turn the screw. It’s only alum and is easy to mess up. It also is intended to remove by screwing in, not out. But you don’t have that luxury. It is also the WOT stop, so by moving it you will change one of three important calibrations.

I would not advise that you do this, and highly doubt it will fix your heat soak issue which is likely some other issue.

You also know that there are two inner screws that are interdependent, right?

[JOEPROPER]

There was a very recent thread about this. Search it. It wasn't long ago. Maybe a few weeks.

[brant]

Please don’t touch the mps without an afr and a running car

If you do you will then have to pay to have it rebuilt/calibrated

[Bleyseng]

Please don’t touch the mps without an afr and a running car

If you do you will then have to pay to have it rebuilt/calibrated

(IMG:style_emoticons/default/agree.gif)

[bdstone914]

@Dredwin

Test it for vacuum and electrical function.
Dont mess with the screws without the knowledge and tool to calibrate it.
I too doubt the heat soak if an MAP sensor issue.
Where it is the fuel pump?

[Dredwin]

@Dredwin

Test it for vacuum and electrical function.
Dont mess with the screws without the knowledge and tool to calibrate it.
I too doubt the heat soak if an MAP sensor issue.
Where it is the fuel pump?

Fuel pump is in the front. I was taking the advice on another thread that recommended it. I know it needs adjusting by a pro, which was the plan. Except my 914 with a V8 decided to break down and I need a new tranny. Depending on the final cost of that repair would impact me buying tools and figuring it out with the help of this forum or turning it over to the shop. I was looking for a quick fix for the heat soaK. There are other options that I read about.

Walking away from fiddling with the MPS. Thanks all

[Bleyseng]

Add one of those CHT extenders to help with heat soak.

[JamesM]

I saw that but can’t access the inner screw because I think of this cover. I know I shouldn’t mess with it without a special meter but my wife is dying to go for a ride and it won’t restart due to heat sink.

I just want to be sure I’m not breaking it if I muscle this screw off

It sound like you are trying to make your issues worse.

1. Temperature related issues have nothing to do with MPS adjustment.

2. If its driving fine once started, your MPS ant broke (so dont "fix" it)


Assuming your issue is that the car start fine when cold, but not after a drive/hot, and your have already relocated your fuel pump to the front trunk, try this:

Next time you are having the hot start issue, rather than attempt to crank the engine just power cycle the fuel pump (key on so the fuel pump runs 2ish seconds, then key off) 10 or so times, hit the accelerator pedal a few times during this process while the key is on as well. Then try to start it and see if the starting situation improves.

Also if possible, always run ethanol free and non winter formula gas.

Im not sure what your issue actually is, but living in a place with very hot summers and high altitudes I have seen hot start issues on perfectly running 914s (even with the FP relocated to the front trunk) due to todays crappy Ethanol gas boiling in the fuel rails. If your pump is under the tank cycling the pump/hitting the accelerator is usually enough to
eventually get the vapor out of the lines and cooler gas into them without having to wait for the entire engine to cool down. If the pump is still in the engine bay you are most likely SOL until you can cool things down. For me the problem pretty much completely disappears as long as i stay ethanol free

https://www.militarytrader.com/mv-101/notes...-other-gas-woes

whatever you do though, dont open the MPS for this issue, it will just make your problems far worse.

[ChrisFoley]

In my experience, a marginally lean fuel mixture can cause hard starting when the engine is hot.
Backing out the center diaphragm screw of a factory adjusted mps by 1 to 1 1/2 turns is a proven way to correct the cause.
Another related issue that is often mitigated by the same adjustment is light bucking at cruise speeds, which may be an indication of lean misfire.

It isn't hard to disassemble a MPS to make this adjustment, only takes 1/2 to 1 hour. There's no need to make it adjustable in the car unless you have a WB O2 sensor and want to play.