Inlet Manifold Gasket - 2.1 MV Carb.

[chewbacca]

Hi all

I've come a bit undone on gaskets again. The gasket kit that has come with the new engine, has 2 of each of the following gaskets with it.
The one on top of the picture is much thicker that the lower one, but both match up to the inlet manifold in shape. 

A quick google shows the top one as probably being correct, but if that's the case, where does the lower one go? I've fitted it using the thicker gasket, so I'm hoping I don't have to remove it again.



Thanks for the advice everyone.

Cheers
Chewie

[Mocki]

You only need one sort , the kits often come with both types. 
 

[chewbacca]

Cheers mocki, that's great news.

Might be coming off again away. The heater plate draws about 20 amps, so I'm not quite sure that can be right! Gonna test it through the relay in the next few days, see if that's any different. I don't see why it would be though. Starting to think I've disturbed the wiring when I popped the heater cover plate off

[maxstu]

Perhaps the thin one is for Digijet or Digifant inlet?

[Mocki]

Twenty amps does seem a little much .... I’m looking for data .....

have a read here viewtopic.php?t=147802

seems it is a 40 amp relay 

[chewbacca]

I'm sure it was fused on the feed to relay with a 15a fuse. That fed the carb heater as well as the inlet, all on the same fuse.

I took the cover plate off the heater when cleaning up the manifold, so I'm now worried I've damaged something in there and caused a short.

To test, I've put the feed wire to the heater plate straight to the battery, via a fuse. A 20amp fuse glowed, but didn't quite blow. A 15amp fuse popped straight away.
The resistance across the heater is none existent, but I guess that could be right. I expected something, which is why I tested it.
It is getting hot, IR temp gun put some of it at over 80 degrees, but some of it not really heating up at all. Thinking about it, I guess that might be an indication not all the heating elements are working.

[Mocki]

I have a good manifold in the stores, I will take a measurement tomorrow if I get time ... it’s got me thinking now 
 

[Mocki]

In  that thread I linked above the last post says 

The replacement hedgehog that I bought has arrived, so I did some measurements just to see if it's working. On my kitchen floor in open air it reaches a steady state current of 10A - rather higher than the 4x0.37A I was expecting. With hindsight this is obviously because the hedgehog casting is a very effective radiator, so the PTC wafers never get to their maximum temperature and their limiting resistance. When the hedgehog is sitting in the manifold below the cold in-rushing air/fuel mix the hedgehog will likely stay even cooler and have an even lower resistance, meaning it'll draw even more than 10A. That's quite a big chunk of current. It's a good job this heater switches off once the water gets up to temperature.

 

[chewbacca]

I definitely need to strip it down me thinks. Appears I've killed it.
Any links to how it comes fully to bits? I've got as far as popping the wire ring out, but it was left in place at that as it seemed stuck.

[chewbacca]

Just a thought, should I get more gaskets now, since I have to remove the inlet, or can I reuse these?

[Mocki]

Reuse them, they haven’t been hot yet 

[ajsimmo]

Carb manifold use the thin gaskets. It's the injection runners that need the thick plastic sandwich gaskets.

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[chewbacca]

Carb manifold use the thin gaskets. It's the injection runners that need the thick plastic sandwich gaskets.

When you say "thick plastic" both of the ones I have are the traditional "cardboard" type, for want of the correct term. One it just much thicker card than the other. I presume the ones you mean would be very different to these?

[chewbacca]

So ignoring the gaskets for the time being, I've been investigating the heater plate, but forgot to take photos. 

I've had the manifold back off & the 3 bolts off of the heater cover. I'm guessing that the whole heating element should come out at this point, but it's well & truly jammed in there. I decided to leave it where it was.

I measured the heater resistance at this point, red feed wire to an unpainted section of the manifold. It's was still about 0.5 ohm. So, still sounds like a short somewhere.

Next the giant C clip thingy came out, which allowed the plastic cover to come away, revealing 4 little discs. On the inside of the plastic cover are 4 springs, all linked together, which push down onto the 4 discs. These springs are connected to the red feed wire.
Thinking that one of these discs must have gone short circuit, I measured their resistance. Each sits at about 2 ohm. Going back to my school days (which was in Mansfield, so...) I think 4 resistors at 2 ohm, in parallel, would indeed give me the measured 0.5 ohm for the heater as a whole.

Since I know it gets hot, I'm guessing it must be ok. Right? So I spent a bit of quality time with Google & it sounds as though the resistance will increase as the discs get warm. Ok, back on the bus with it & testing time again.

With the manifold mounted, the resistance is around 0.5 ohm still, but measured to an earth on the bus. I powered the heater up with a length of wire again, via a 20 amp fuse. Same again, the fuse glued, but didn't blow. After a 1 or 2 seconds, it stopped glowing. I kept it all connected for around 30 seconds, then measure the resistance again, as quickly as possible. It was dropping very quickly, but I saw 10 ohms hold itself for a second, my meter couldn't really give me a reading before that, the resistance must have been dropping too quickly. 
My take from this though, if it's drawing 20 amps to start with when the resistance is 0.5, it must be drawing lots less when at 10 ohms.

If...
I = V / R
I = 12 / 0.5
I = 24 amps (I bet the voltage drop brings this down, but by the time the engine starts & voltage increases, the resistance is up)

So, when running, plus lets say the alternator got carried away...
I = V / R
I = 15 / 10 (resistance could be even bigger than 10, but that's all could measure)
I = 1.5 amps

I wish I had a method for measuring the current through this heater, but I've nothing that size. 10 amps is the max I can measure & I would guess that's a struggle for the poor old multimeter.

Now the confusion. I've had this heater wired through a 15 amp fuse for years now, plus the heating element on the carb is on the same feed, so will have been using some current as well.
SO WHY DIDN'T THE FUSE BLOW! 

My only thinking at the minute is that the relay has some sort of current limitation, but that seems really unlikely to me. It would just get turned into heat. There's no way it was the wiring, the cable I used would have sat at 50 amps I would think, let alone enough to pop a 15 amp fuse. Basically, I'm confused.

The current plan is to wire it up as it should be & see if the new 15 amp fuse pops. If it does, stick a 30 amp in there since in stock form there is no fuse at all. 

[ajsimmo]

You should have these 3 pairs of gaskets in your set. Thick ones for injection, thin ones for carb DG, and the small hole ones for the DF.

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