MA12 Transplant Problem.

[porkpie700]

I have just replaced my 1989 MA10 with a 1993 MA12 and I’m having problems setting it up.
In its original car the MA12 was set up with a cat and exhaust gas recirculation system (EGR), with the electrical carb and computer. None of those parts came with the engine and setting it up in that way is not an option.
So I’m using the standard carb and distributor from a low mileage MA10 (also from an 89' car but not mine).

The MA12 is currently all bolted in and everything is connected up correctly, all hose pipes and vacuum line are new as is the dizzy cap and rotor arm, spark plugs, cam belt, thermostat, inlet and exhaust manifold gaskets.
The engine starts and idles, the choke & idle-up solenoid work as they should, but the engine runs slightly rough and un-evenly, popping and burbling every few seconds. When i try to drive it the engine can't seem to pull the car so it has to be given plenty of revs and be moved very slowly or else it stalls.

I've adjusted the timing on the dizzy but that doesn't seem to help it much, move it one way the engine revs up and knocks, move it the other way & it splutters and wants to stall.
The mixture I’ve also adjusted as it seems to be overheating and stinking, I've turned it a half turn IN (richer) because from what i understand the leaner the mixture is the hotter an engine burns. Whereas a very rich mixture just chokes it up (At least this is how I’ve always thought it was).

I know some of you out there have swapped your 1L's for 1.2's before so if any of you guy's have had this sort of problem before and know how to cure it then I would greatly appreciate it, thanks.

 

[Ed]

Have you got the firing order right? It should work fine. If its over heating at idle I would say something is wrong with that engine. There is no way it should do that regardless of idle mixture or anything else.

 

[porkpie700]

The firing order must be right, i put the leads on the cap in the right places and the distributor can't be facing the wrong way surely or else it wouldn't even run. I've had a misfire due to a loose lead before and this blip is nothing like that. More like a nudge or a little kick every now and then. If I rev it up fairly high it really doesn't like it and won't idle afterwards, have to hold the throttle on for a little bit until it settles back down.
As for the overheating, the temp gauge sits around one quarter and so should be normal but the inlet manifold is so blisteringly hot that it may well be vaporising the fuel. I know the MA10 mani used to get hot but this one is twice as hot, but it is a 1.0L carb so that's why I assumed that the mixture would be out. After all a bigger engine would need more fuel you'd think, so I thought that's why it may be lean.

I know that this engine looks like it's had it water pump taken off at some time in its life, weather or not it was replaced I’m not sure. The exhaust smoke is blue-er than I would consider normal but it's still moist and drips condensation like it should.

 

[imp124]

am i right in saying the 1989 distributor has a vacuum line coming off it and the MA12 EGR didnt (electronic igniton) if so are you sure this vac pipe is connected correctly, also check the condensor and points inside the distributor.

 

[Ed]

Still wont cause this level of running problems. The inlet manifold is designed to get that hot. It has water flowing through it.

Look at the float chamber on the carb it should be up to the half way line. The pump may not be supplying enough fuel. Do a compression check too.

 

[porkpie700]

am i right in saying the 1989 distributor has a vacuum line coming off it and the MA12 EGR didnt (electronic igniton) if so are you sure this vac pipe is connected correctly, also check the condensor and points inside the distributor.

Yes it does have the vacuum line on it and yes it's connected right and works fine. I don't have points dude, it's the electronic ignition type used from 89' onwards (facelift model) you're thinking of the old collette era model. I know the vacuum is fine coz i pulled it off to check and the engine nearly stalled, put it back on and the engine came right again.

I'm thinking of changing the carb with the one from my old 1.0L since i know that one works fine but if that doesn't cure it then i'm tempted to say that it might be the head gasket since it's a 117k engine (allbeit they were motorway miles).

 

[Ed]

Have you done a compression check? What do the plugs look like? Put new ones in run it for a bit then take a look. These things are dead simple really so you should be able to find what's up without too much difficulty.

 

[porkpie700]

Still wont cause this level of running problems. The inlet manifold is designed to get that hot. It has water flowing through it.

Look at the float chamber on the carb it should be up to the half way line. The pump may not be supplying enough fuel. Do a compression check too.

Just changed the fuel pump and still no joy, as soon as the engine gets warm it wants to quit.
Also i've just put some new plugs in today, i used old ones for the first few starts as i had sprayed WD40 into the ports when i first got the engine, so i didn't want to cack up the new plugs right away.

When it starts from cold and the choke is on it seems to be smooth and sweet, with a nice whine when you rev it, just as soon as it gets warmed up is when it starts acting up. Just now it's done a few hissy pops out the back which is new, and it has now drunk the expansion tank.
Haven't done a compression test as i don't have the gear to do it, noticed a very tiny amount of white goo on the oil cap but the coolant and the oil are still clean.

I'm going to change the carb on it on monday so i'll see what that does, the flap on the one thats on there seems to be sticking a little in the right (passenger) side chamber.

 

[imp124]

if its drank the expansion tank and there is some white gunk on the oil filler, i would do a compression test just to be sure, the kit only cost around £20 (at least mine did) or most garages can do it cheaply

 

[Ed]

I think its the carb, manually push the choke closed and see if it runs better again when warm. It sounds to me like its leaning out and missing when hot. Don't worry about the expansion tank. They never seem to tell anything useful.

 

[porkpie700]

I did that check last night Ed and it revved up but died out if i gave it any throttle. So i changed the carb this morning with the one from my old MA10 and it hasn't stalled as it would have, stopped stinking like cooked oil too.
It actually drives now and once it's moving you can't hear or feel the engine, very smooth, but something is still a little off. It seems to just miss/die slightly every 5 secs or so when idling and if it's revved suddenly or repeatedly there is a definate loose knocking sound and an odd crack/click (kind of like if you put some force on a stubbern bolt and it just gives and starts turning).

I forgot to ask before, i'm using the origional MA10 radiator. I couldn't get the MA12 one for it, would this make a differance i.e. higher pressure or do they both work fine with each other?

 

[Ed]

Both rads will work fine. Ok so was definitely fuel problem. Can you see the fuel level on the float window? Should be half way.(though I suspect it probably is) Sounds like your getting close now anyway.

 

[porkpie700]

Yep it's level with the center marker. I had to use some instant gasket when i put the carb in, it looks like the gasket was allowing coolant to be drawn into the inlet manifold which i'm sure didn't help lol. I'm going to go over everything again a couple more times today and see what's what with it. Thanks for that Ed.

 

[porkpie700]

Problem Sorted

The new engine's all sorted now, turned out to be the mixture. I took off the limiter cap and cut the screw head to take a regular flat-head screwdriver. It was running way too rich, when the engine started the float level went way up past where it should be. All tweeked and running fantastic now, so thanks for the advice guys it is apreciated.

:k10:

 

[imp124]

Glad you got it running well, how is it compared with the MA10?

 

[Ed]

IMO MA12s feel choked. The inlet manifold and carbs are really restrictive on a stock MA12 engine... They dont like to rev like the MA10. porkpie700 experience may be different however, they are a lot more torquey however

 

[Ceirwan]

After coming back from driving other cars for a while I'm inclined to agree with Ed, it feels like its struggling to rev sometimes, or that something holding it back...

Glad you got it sorted mate

 

[imp124]

i agree that they are more torquey and quite restricted, especially after seeing the ST engine and inlet manifold

 

[porkpie700]

MA12 Performance

Obviously my MA12 is NOT running on a standard 1.2 set-up, it WAS a Catalysed engine but now it is NOT. It's also running on a 1.0L carb (which i believe has bigger jets) and inlet manifold, the exhaust manifold is also from a 1.0L, the distributor is from a 1.0L with a 1.2 rotor arm and cap (though i think they're the same). Other than changing the timing belt, thermostat and all gaskets excluding the head gasket, i have not tuned the engine in any way (other than polishing the insides of the two manifolds) and all parts were genuine nissan.

Basically what i'm trying to say is that if you have a MA12 and you engine performs differently to mine it doesn't mean that my motor or your's is wrong, just that they're both unique. So don't be accusing me of talking BS basically.

I have so far covered 70 miles and that engine is a world apart from the MA10. For a start it's so quiet that i can neither hear nor feel it when cruising at a set speed. It feels very refined and i would compare it to a quick K11 (at least one of the three that i've driven anyway lol).
The torque is very impressive, especially up steep hills it just pulls away like it's carrying nothing.
As for the revs, when i hit the gas (from low revs) the torque kicks in straight away and it push's me back into the seat, when the revs build up it just growls and a keeps pulling. No problem with revs but i personally don't like taking any engine too far up in the rev range.
I've noticed that it likes a drink when you prod it though lol, but that's a fair trade off for what you get.

I would like to add in defence of my old MA10, it was a fantastic motor and when it wanted to be it was smoother than you could ever ask of a 20 & 1/2year old motor. Just wasn't cutting it on the motorways and the hills that's all, eventually when i get some money together i'll be restoring that engine like i did with the MA12, then it'll get moth-balled till it's needed again.

 

[Shaun]

sounds like a MA12 (Y)