Turbo boost gauge doesn't do anything.

[Trick]

I know I'm probably missing something quite simple. The boost gauge doesn't register anything. If I short out the connections on the orange sender unit, it shows full scale deflection. I fitted a balloon to the pipe that feeds the sender and on idle the balloon was sucked flat, showing a vacuum n(Is this normal?) . When I revved the engine the vacuum went but the balloon stayed flat. (Should it inflate?) The earth to the sender is fine. One of you clever blokes ought to be able to give me a pointer. Or is the sender broken? How do I check this?
Thanks in anticipation
Oh I live in Spain.
John

[hatters]

Wastegate Wiggle??

[Rice crispy]

The gage wont work unless you are driving as far as i'm aware. How did you check the earth? And is it just the gauge not working i.e. Are you getting actually getting boost when you drive the car but just the gauge isn't registering
David

[Trick]

Wastegate wiggle tomorrow. Next job.
I dont know if I am getting boost when I drive it. The gauge shows none. It doesn't feel like it. I can't tell if the turbo is working or not! No idea what it should feel like or sound like if it does work. Have revved it and no pressure is coming from the tube to the boost gauge sender or the waste gate actuator.
Thanks John

[Trick]

Right then. Did the waste gate wiggle after looking at the waste gate actuator found it wasn't actuating. In fact no movement at all. That is now solved. The previous owner had installed a dump valve which wasn't working either. The frequency valve turned out to be broken so I have bypassed this. Even with the boost gauge sender connected directly to the plenum it doesn't work so my conclusion is that it is broken. I think I'll buy a similar aftermarket gauge and fit that, Now that I have solved the waste gate and dump valve problems the car is a lot better to drive. Thank you for the help. John

[epipete]

John,

Check out the March 11 aftersale list, many of them available @ £15.00 each.

Pete

[tigerdog]

Alternately, you could install a VDO 150121 boost/vac gauge . You can use the bezel and glass from your failed Elan gauge and reface as I did in Smaug. This gauge is mechanical - you have to run a length of capillary tube to the manifold, so it does away with the sender and cleans up the look of the engine bay. I can send you the face graphic to print on photo paper if you want to duplicate my setup.

[rip]

The gauge wont work unless you are driving as far as i'm aware.

I think you can get it to work, but you have to accelerate hard...so it will only work for a split second before you run out of revs. That probably won't show you anything useful.

[Pascal]

Hello from the french newbe,

i have a problem that looks like this one here, please advise :
The boost jauge was working properly some days ago, from zero to 0,65 B approximately when calling for power.

last week i found this : when i switch on, but engine not yet turning : boost jauge says 0, 25 B .
Running the engine : jauge says wrong informations from zero to 'full' (more than 1 B).

And today : i switch on ( engine not yet turning) : 0,5 B . engine turning : 0,5 B, and sometimes another value that has not meaning.
I do not feel a difference in the way the engine work, but maybe a higher gas consumption.

Note ! I looked at the pictures in the wiki, and found some pictures of the MAP sensor controller. On my LHD Elan , the centrally located part (on the bulkhead) is almost impossible to reach whithout removing the whole wipers system and its frame !
There is another sensor on the common chamber/intake plenum , i think the MAT sensor. When plugging this one off, the boost jauge says 'full' (more than 1 B).

Could this be a defective MAP sensor damper ( left side of the intake plenum) or controller ?

I would take with pleasure any suggestion to investigate,
regards, Pascal

[GeoffSmith]

Pascal, the boost gauge has its own sensor and a very bad earthing arrangement - check the Wiki.

[Pascal]

Many thanks,
it was just this earth connection that was rusted, now the jauge works perfectly.
I tried to find by myself before asking but obvisously you have here so much experience about the M100 that you know all by heart ... impressive.

Pascal

[Pascal]

Hello again ...

Now the jauge works properly, yes. But the pressure can hardly reech 0,5 b .
Before, it was reaching about 0,65 b.
I wonder if the jauge was a bit injured by the ''more than 100%" signal ;
or if the turbo is really loosing performance.
How to check this ?

My first feeling is a true turbo pressure loss.
( I am not sure because i changed the tyres in the same time, the new tyres stick to the road and i can't play stupid noisy burn- out anymore. Less noise, less power feeling, that could be).

Well, pressure loss is likely true ...
I noticed ''sticky wastegate'' in the wiki, is this the proper path ?

Have a great day,
Pascal