dizzy trouble

[Dude its Robert]

I have a 72 521 with a l20b out of a 79 200sx I think and it has the matchbox dizzy

it started idling funny a couple days ago and then when I turned it off it didn't want to start again without throttling it and wouldn't idle

Then later that day I got it to idle and started pulling plug wires #1 and #4 cause it to run rough but #2 and #3 made no change

It was getting spark when I pulled the plugs but it seemed weak so I did a cap, rotor, plugs, and wires but it still does the same thing

 

Im to the point that I thik I need a new dizzy but I hope that's not the case

 

Please help this is my DD

[Dude its Robert]

Oh and at 0° BTDC witch would be TDC I would think and the rotor points to #1

[banzai510(hainz)]

but #2 and #3 made no change

 

spark plugs good? since you got new wires they are good.

valave lash set correctly on those rocker arms for cylinder 2 and 3. See if rocker wiggles a tiny bit if the cam lobe is pointing straight up.

 

holes in vales or pistons.

 

tighen the intake/exhaust manifold.

 

 

dizzy cant be bad if 2 work and 2 dont unless the start reluctor prong fell off or something obvios you could see.

 

 

no idle is idle jet plugged or the mixture needs adjustment.

521s suck up alot of dirt so replace the gas filter more often.due to the gas fuel hose in wheelwell.

 

fix 2 and 3 first.

 

 

 

if you changed anything let us know.

[datzenmike]

Funny how it's the middle two cylinders. Could be a blown head gasket between them. Not all blown gaskets involve the water jacket and they don't always over heat. A compression test may show these cylinders low compared to the other two. But as Hainz said, check that you have some valve lash clearance on #2 and #3 intake and exhaust first. If tight it too would leak compression. If valves have clearance do a compression test.

 

 

I would say 2 and 3 wires are switched but they don't get changed by themselves. The firing order is 1342.... did you confirm this when changing the wires? .

[Laecaon]

Yea, switch the 3&2 wires. My friends motor all but ran when all wires were reversed.

[Dude its Robert]

Compression is good across all 4 and I made sure I did the wires in the same order as the old ones and confirmed that they are 1342 and I did plugs too

[Dude its Robert]

It has a brand new carb so I don't think that's the issue. That's what I replaced last time it didn't run lol

[Dude its Robert]

So it will idle now but switching #2 and 3 wires did nothing and pulling them doesn't change idle

[datzenmike]

You need compression and spark. This should be easy to fix.

 

What were the compression numbers???

 

Pull wires and stick a plug in the end, lay on grounded surface. Crank and compare spark. Are 2 & 3 different somehow?

[Dude its Robert]

Didn't do a legitimate compression test because I don't have a tester I just did the finger over the spark plug hole version and they all felt good and all get spark ill check again to see if those two are any different than #1 and #4

[datzenmike]

Haha ha . Sorry, that's like having sex by sending a letter. Just not good enough. For a diagnosis you need actual numbers. An extremely bad cylinder could still have 60 PSI and it would be hard to hold your finger in the hole.

[Dude its Robert]

I know lol but that was the best I could do im ganna get a tester tomorrow. But Arnt cold engine numbers a lot lower than actual compression?

[datzenmike]

Compression numbers will be slightly lower cold but not way lower.

 

Did you check the valve lash?? Important that no valves are tight. If they are tight they are not closing properly. Not closing tight will leak compression. It's easier to adjust valve lash than remove the head to find out it's the valve lash.

[racerx]

get a compression checker..who knows you may even find one cheap on Craigslist.  If you do buy one get the screw in type.

[Dude its Robert]

I think my uncle has the screw in kind so ill have to double check

[racerx]

You want to get a good reading...also get a piece and paper ready and write down comp. Date too so u have a history

[Dude its Robert]

About 120 psi every cylinder

Spark on all 4 and the spark didn't look any weaker on #2 and #3

[racerx]

120 seems kinda low.  I think 170 is norm and about 150 is good. Did you use screw in type of comp. checker?  what color was your spark?

[Dude its Robert]

Yeah it was screw in and that was on a cold engine. Spark was orange

[racerx]

try warming up car first before doing comp. check. 

[Dude its Robert]

Its only running on 2 cylinders -_-

[banzai510(hainz)]

have  you iopen the valve cover and do a valve lash adjustment?

Simpler yet is just make sure the cam lobe is pointing up and if the rocker arm wiggles a little you know the valve is closing. ck this on all 4 rockers that are #2 and #3 cly.  if they loose you know the valve is closing. if tight then fix that first.

 

 

If it wiggles you know valve is closed and compression is low because there is a crack in valve valve seat, piston gasket bad. or just something Im not catching here.

I assume the sparks plugs are good and the wire are not sprking out to ground.

As this just happen to me yesterday. My #1 plug wire are arching out on the head making it run on 3 cylinders.After I spray engine degreaser on there.

So Now I got to get on Amazon.com and get soem more NE64 NGK wire sets.

 

 

ps I think 120 is low on the reading but it should still run on all cylinders even at 120.

[Dude its Robert]

I have not checked the valves yet im ganna hopefully do that tomorrow and it has brand new plugs and wires so I doubt its grounded on those two cylinders