780rx7

So my son and I swapped out the motor on his 80 rex because the old one seized. We finally got everything hooked up, fluids in etc. and tried to start it. It wants to start, exhaust is coming out, but she won't quite light. If we pump the gas, we have the most success and almost starts which leads me to think that it isn't getting enough fuel. In taking the plugs out though, they are quite wet with fuel. There is good spark even with the wet plugs. The new motor is a used one with supposedly 66k kilometres on it. It is supposed to be a canadian model, but in installing it, I'm pretty sure it is a california model or at least the carb and vaccuum system seem to be. The motor came with the carb. I'm thinking that the carb might be gummed up as it has obviously been sitting a while so I may put the old one back on the new motor and see if this solves the problem. I have two concerns though. One, when we are turning it over trying to start it, the motor seems to catch (seize) every once in a while. It cranks normally then all of a sudden stops dead for a millisecond and then goes again. Is this normal??? I'm worried we are going to seize it as we are trying to get it going. Also, is there anything I am overlooking or confused with? Can you have wet plugs at the same time as not getting enough fuel? ie, can there not be enough fuel to quite fire up, but enough to make the plugs wet because there is not fire? Also, does it make sense that she wants to start with pumping the pedal or are we just plain old flooding it? IT won't catch at all without pumping the pedal.

sorry for the long winded post. We have had so much down time with this car this year but with the help of this forum have fixed everything our self, but man are we frustrated at this point. The look on my sons face as we are trying to get this baby to start after so many hours and dollars swapping the motor out is tearing my heart out. He has been so patient with it as we have sorted out all the problems and loves this car.

ANyways, any help or advise would be appreciated.

Thanks in advance,\

Neil & Liam

Jeff20B

iTrader: (13)

Ignition probably isn't set up right. Is the distributor "stabbed" in correctly? Do you know the procedure?

780rx7

thats a good question, never thought of that. I just took it out of the old one and put it in the new one. It seemed to fit fine in the same orientation as the old one.....? To answer your question, no I don't know the procedure. I'll look it up in the fsm, unless you have any advice for me on that.

THanks so much for the reply.

gerald m

Even with a flooded engine pumping fresh gas into it will sometimes make the engine fire a few times before going back to the no fire problem ..You could try the deflood procedures get it dried out real good then try a little starting fluid .. Might help

780rx7

Thanks guys!!!!

I snuck home from work, re-"stabbed" the ditributor, deflooded the engine, put in fresh plugs and (wait for it....) Yes!!!! She is purring like a kitten. I know, I'm a bonehead for not thinking about setting up the distributor correctly.

Again, I can't say enough about the help we have received on this site. Thanks so much for everything!

Oh, a question on the timing marks on the pulley. I'm guessing the red mark is the trailing mark? The fsm says the yellow mark is the leading mark. this was tough to find although there is a faint beige blob on the pulley about an inch before a red mark. I set it at what I am assuming is the yellow mark. The manual doesn't say what colour the trailing mark should be.

Thanks again!

Neil & Liam

gerald m

Yea you got it the YELLOW mark is the first one the red is second .. there should be 2 notches in the pulleys where the paint is .. maybe you could redo the marks for future timing work ..

780rx7

Thanks again. So another puzzler to me..... On the old motor the temp gauge in the instrument cluster didn't seem to work. We attributed this to a burnt off wire where the yellow wire plugs onto a spade connector at the engine block up near the clutch slave cylinder. On the new motor, we made sure to plug this in. After starting the motor and warming it up I noticed that the gauge still wasn't working. I looked and the yellow wire was burnt right off of its female spade connector on the block again. The plastic of the connector was still plugged into the male, but was melted a bit. Does any-one know what would cause this to go on both motors? Also, there is a black wire (green stripe) with a female spade connector coming out of the wiring harness at the same place that this yellow wire comes out, but I can't find anything to plug this into? It's not the black/green wire that goes down to the oil pan for the oil level unless I am missing something.

Any help/advice would be appreciated. I'd like the temp gauge to work.

Thanks guys,

Neil & Liam

gerald m

I'm not much of an electrical guy one of our members SATCH seems to be very good at wiring problems maybe when he has time he might be able to help you out. ..

clykins

iTrader: (1)

After reading another post I might suggest testing for a bad ground. I will see if I can find the post and give you a link.

clykins

iTrader: (1)

Here is one. I hope this helps. Good luck.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/how-test-wire-find-short-275086/

mortiky

just to make sure that your gauge is functioning, just take the wire off of the sending unit and jump it to any known "good" ground and if the gauge and wiring are good then the temp gauge should jump all the way up to the hot and dummy light should illumn. if this happens then most likely you have a bad sending unit. if not the you either have bad wiring or a bad gauge, or both....

DivinDriver

iTrader: (15)

There's another thread detailing the gauge problem, isn't there?

780rx7, I can help you ident that motor build as Cali or non-Cali easily... if it has an EGR valve top center on the engine, and if it had five gas-passage holes (three front, two rear) in the exhaust manifold gasket in addition to the four bolt holes, it's an 80 Cali motor.

780rx7

Yes, DivinDriver this is my original post, but posted the burnt wire one a couple days later as a specific post on the problem. Thank you for your generous advice and also to every-one else for there input as well. I hope to take another solid look at this issue this weekend. I'm thinking it is a bad sensor as well, because the wire on the old motor was about 3" long from the block out and the plastic connector wasn't melted looking at all which leads me to beleive the old one was just broken while the new one is fried. I looked at the 15A fuse and it is fine as well the gas gauge does work. I'll look into the diagnosis a little further on the weekend and report back.

A question on the guage test....will shorting the yellow wire to ground while the key is turned on risk the health of the qauge/circuit or is this o.k. to do. It sound like a great idea and an easy way to test the gauge but I'm worried that I may fry something.

Thanks again for everything everybody!

Neil

ty97206

I have always had to pull start a new engine. I don't know why but its always worked and started right up wry key after that..... try it out maybe?

DivinDriver

iTrader: (15)

I wouldn't recommend it, not knowing the max current the gauge filament can handle. Might be OK, or might cause the heating filament that drives the needle to overheat.

Proper way to test the gauge would be to hop down to the local Radio Shack, get a 68-ohm 1/2-watt resistor ($1 for a pack of five), and use it instead of the sensor to connect the sensor lead to chassis ground. Should give you a partial-scale reading somewhere around half-scale or higher. Don't hold it in your hand, as it could get hot.

mortiky

i've never blown one doing this, but i wouldn't leave it connected long just long enough to see if it works. however he is right the best way would be to use the proper rating resistor or even a potentiometer that is within the range of the temp gauge. if you have an extra hand though you can have your assistant ground it out real quick while you watch the gauge and dummy light and if it comes on and gauge starts to climb. so if a 68 ohm gives you half you could use a 100 ohm pot to test the gauge..

780rx7

So, I repaired the wire, put on a new connector, replaced the sensor with the one from the old engine and fired it up. The wire didn't burn off or melt at all. AFter running it in -5 (celcius) weather for about 15 minutes the temp gauge moved to the very bottom of the range and stayed there (just touching the cold line). As I was by myself, I didn't get a chance to test the actual gauge but I intend to. It looks like it works now somewhat though (thanks for all the help!). Should it warm up more than that though? I dind't get the chance to road test it yet so maybe it will warm up past the bottom mark when it gets some rpms up but it seems like it should get warmer than that. The t-stat is new and is a 180 degree (or thereabouts - I can't remember exactly) unit. PArts guy recomended it as it was the middle of the three available...

And yes, it is a California car. It has the EGR valve. The other wire that I couldn't find the use for was for the oil thermo sensor (non-existential on a Cali car).

Anyways, thanks again for all the help. I'm paranoid of blowing this thing up.

Neil

DivinDriver

iTrader: (15)

Everything may be fine at this point; the factory gauges are notorious for not being "highly calibrated." It's responding to the sender, which is responding to heat. My car at normal fully-warmed idle on a 70-degree day usually sits only about 1/4 - 1/5 above the bottom of the range line. Cold weather would make it read colder.

In the FSM for the 80 ('body electrical' section, page 15:6), it gives the following resistance values for testing the gauge - - Mazda had a "testing box" for this, which was nothing more than a series of resistors & switches in a box.

"C" hashmark = 233 ohms
Bottom of range line = 104 ohms
top of range line = 21 ohms
"H" hashmark = 16 ohms

You could test the sender by disconnecting it from the meter, and then hooking an ohm meter from the sender terminal to ground. With the engine warm, you'd want to see something of around 100 ohms or less. Then compare that measurement to what the gauge is showing you, based on the above ranges.

Or you could use resistor(s) to simulate the sender output as I described before. Either method will give you a good idea if stuff is working, but resistors are a lot cheaper than an ohm meter of you don't have one.

780rx7

DivinDriver you truly are one generous guy. Thanks for the time and effort that you have taken (and every-body else) in response to my issue. I haven't actually had the chance to test the gauge yet, but we took her out last night and the temp gauge climbed to the bottom of the range zone in o degree (32F) weather so I think you're right, everything seems to be responding.

If you guys have the patience for me, I have run into another few issues, which are probably related. As discussed above, this is a new to us/used motor. When starting from dead cold with the choke pulled out, the engine fires up right away and climbs to about 2500 RPM but then seems to load up and isn't able to sustain the idle. It just seems to get flooded. With some work on the pedal, I keep it up at around 3500 and it seems to be able to clean out a bit and will hold a rough idle at 2000. The manual says to hold it at 2000 for about 2 minutes and then push the choke in and let it idle which we are able to do and it runs smootlhly with the odd hicup. The old motor/carb would take itself up to 3500- 4000 easily and run cleanly with the choke in until we put it to 2000. The other issue is that on the street, the motor seems down on power in the higher RPM's by about 10-15 percent easily. It has very linear power with perhpas more bottom end, but just seems down quite a bit with no "hit" at all in the upper RPMs. It also runs a little rough and chugs at around 3500. This new motor is all stock but has a full Racing beat exhaust system that we had on the old motor.

I'm wondering if this could be a timing issue (I haven't set it with a timing light as I don't have one). I have played with different distributor positions a bit and have it set roughly where it seems the best which is the same position as the old motor. The other thought I had that DivinDriver pointed out is that the RB header gasket may not have all 5 holes for this california car (I didn't check when we re-assembled). Could this be blocking the exhaust flow?

I know this could be a plain carb issue, but wanted some feedback before diving into the carb. As you guys can tell, my mechanical diagnostic aptitude is limited. Give me a set of wrenches and a manual and I can do anything, but diagnosing is pretty weak.

Anyways, she is on the road and the boy has a smile on his face, but its not quite right and I'm still paranoid. Thanks for listening and I understand if you guys are tired of my inane questions!

Neil & Liam

DivinDriver

iTrader: (15)

Do you need to pump the throttle to keep it idling, or just hold it open a bit?

On the exhaust gasket: you don't have any issues there, since the RB header flange works as a block-off plate on the other side of the gasket.

You will probably want a block-off plate for the EGR; take the EGR valve off and save it (working ones are worth some money) as with a header in place it can't actually do anything. Make sure you cap it's vacuum source, too.

Did the carb come with the motor? Have you removed or blocked off the other emissions equipment (ACV, air tube, air pump) that are made unnecessary by the header?

780rx7

Hi. I don't need to pump the throttle, just hold it open to keep it clear and to keep it from loading up for about 30 seconds or so. I'm assuming it's loadin because it starts to emit fuel laden exhaust. I suppose it could be not getting enough fuel although that doesn't feel right.

I've removed all the air pump/air hos/ACV etc and installed the rb block off plate.

Will removing and capping the EGR help this issue?

The carb came with the motor. It starts excellent cold or warm (way better than the old one when warm). I suppose it could be partially clogged jet? I was going to try adjusting the air mixture/idle speed?

What do you think about the timing?

Also, right now it idles at 1,000 after starting (warm) but after driving won't go below 1100-1200.

Thanks!

DivinDriver

iTrader: (15)

I don't think blocking the EGR would matter in this case. Sounds more like a mixture issue... either a mis-adjusted choke or fast-idle, a vacuum leak or some other issue with getting the right AF mix while on choke.

If holding the throttle open slightly is improving the behavior while on-choke, that sounds like a too-rich condition. Either the choke is closing too tightly, there's too much fuel in the mix, or the throttle plates aren't opening enough while under choke. Or you've got an air bleed or two that are a bit gummed up.

Does manually easing the choke in a bit, thereby opening up the choke slightly, improve things, make it worse, or no difference?

780rx7

Morning! I tried pushing the choke in a bit last night and it didn't let the engine climb any better, the rpms just climbed lower to about 1500 with the choke about 1/2 to 3/4 out. It may not have flooded though, couldn't really tell. Our method of starting seems to work though. It starts immediately and then with a little extra throttle, cleans out pretty quickly and then it will run at 2500. If we don't give it throttle, it starts to load up and the rpms keep dropping and it seems to be running really rich. It's just weird as the old one ran cleanly right away at about 3500. Maybe 2500 is more appropriate? It is defintely down on power when driving it though. It's like it won't rev quick enough. If you stomp on the gas at around 4,000 in the appropriate gear, it climbs up through the rpms fine, but with no punch at all. The old one would come alive in this rpm range where this one seems a lot more linear and slower. We ran a can of seafoam through the gas, but added it with about 5/8 of a tank, so the concetration was probably pretty weak.

Anyways, it seems to run reliably albeit not quite right. We will keep playing with it, unless any-one has any ideas. Thanks again for all your help.

Neil & Liam

780rx7

vacuum switch!! This motor is a cali motor which is supposed to have a vacuum switch. I have this port capped off as it was capped on my original rats nest. Could this be the issue??? I just stumbled across this in the fsm!

780rx7

bump