redfb

ok for the past 2 months i have been trying to figure this out meanwhile sharing a car with my wife

i have an 85 SE with RP exhaust, bonez intake, jacobs fc ignition, jacobs coil packs, the engine has roughly 80k on it.

The thing it's doing is when i start it, it will run for aprox. 5-10 seconds then die quickly. If i try to give it gas it won't do try to rev back up or anything. I tried driving it and it just died even with me mashing my foot all the way down to the floor.

I've tried looking at the AFM the flapper works and when it dies it just kinda closes as it should when you cut the engine off...the fuel filter was REALLY clogged up so i replaced that, cleaned the screen in the fuel pump, replaced rotor, cap, plugs, wires, and filter.

It's kind of frustrating because it's my daily and my first rotary too. Also no one around works on the dang things so i can't just take it to a shop. If you guys could help me out my wife and i would greatly appreciate it.

here is a video of what it's doing
http://www.youtube.com/watch?v=tksSIXm1_OU

Crit

iTrader: (6)

Don't sweat the two plugs, they're both diagnostic. The one with the black rubber cap is a short connector for the fuel pump. If you short that plug, the fuel pump will come on when you turn the key. It currently only runs if you're either cranking or if the flapper door is away from its rest position. This just cuts the fuel pump off if the engine dies and the airflow stops.

The green connector is used for setting your throttle position sensor, but it's typically just a drivability thing. You've got bigger fish to fry before you should be worried about your TPS.

So lets figure out why your engine dies. Personally, I'd check the fuel pressure between the firewall and the two fuel lines that go to and from the block. Then test your fuel pressure regulator. It's triggered by one of the solenoids on top of the engine, and it cuts the fuel pressure down at idle so the injectors can properly deliver short spurts of fuel. You need a regular EFI pressure gauge, which will go to 80psi or so, and it needs to end in a 5/16 Tee. You can then slip the tee inline with your fuel supply line and check your pressure.

If your pressure's good, then you can go to AutoZone and get their free loaner set of noid lights. You'd basically pull your intake manifold off, pull the connectors off the injectors, insert the lights, and see if the injectors are getting triggered or pulsed like they should.

If you have pressure and signal, then your problem is either ignition-related, compression-related (you do have good compression, right?) or you've got stuck or low-flowing injectors.

mazdaverx713b

iTrader: (91)

along with what Crit had advised to do, are you sure you are getting good spark? have you tested the afm voltage output with a multimeter? will the engine run longer by spraying starting fluid into it? did you checkfor vacuum leaks? vacuum leaks are a BIG problem and can cause the 7 not to start. in most instances though the vacuum leaks will cause a high or erratic idle. if your spark is weak or not present or you are getting no fuel, a check of the trailing ingintor is in order.

redfb

i hope the compression is good, i haven't checked it yet does autozone have loaner compression check tools? We just had a baby so i am trying to keep my expenses to the minimum but i do understand that i need certain tools because i've already spent over 100 bucks replacing things i thought i'd be but it isn't


i tried to check for vacuum leaks but i couldn't find any on it. I haven't check the AFM voltage and was hoping it was the afm or fuel pump. If starter fluid makes it run longer what does that mean?

bliffle

Almost exactly the same as my problem. I looked at your video and the only difference is that mine runs a couple secs longer and i have to rotate the key to OFF before trying again.

My thread:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/se-died-warning-lights-came-tach-needle-kicked-up-starts-few-seconds-756832/

hanman

From watching your video, I would say that my guess is fuel. It acts like you have enough fuel to start it, but it quickly runs out.
Check the values on the AFM first. Use a digital multi meter. If you don't have one, you can get a cheapy anywhere. Look in the service manual for the way to check it. The symptom of a bad AFM is the car will start and run for a second or two then die. I have never had a bad AFM, so I don't know how long it runs before it dies, but that's where I would start.
BTW, your car is not turning over fast enough either, bad battery cables or bad battery, but again that is for another day.

If the AFM checks out ok, I would try the pressure gauge on the fuel system.
If you were having trouble with rust in your tank and a plugged fuel filter, it may have plugged up again. I have seen that happen many times. If that is the case, I would drain and drop the fuel tank and take it to a radiator shop and have it flushed out.

bliffle

I took my AFM out and tested it per the manual and it tested OK. But I PMed with an FC owner who told me he never solved the problem but by shorting that test point (with the black hood) he's been running the car OK for a couple years.

I'm gonna go try my shunt for that test point in a few minutes.

The fuel pump jumper didn't work.

I could hear the fuel pump running when I turned the key to ON, but it started and died after an even shorter run than before.

I had high hopes, but... I was prepared for success: I had a pic of the nice little shunt I made, you know, so I could brag on the forum. But, alas!

I may try getting an AFM off ebay or forum classifieds, but unless some OTHER function of the AFM (unknown) is causing this problem I'm not hopeful.

I'm going to run some more voltage tests using 2 or more voltmeters because I'm very suspicious of the sequence of events. When my SE dies the tach immediately goes to zero. Instantly. To me this suggests that the problem is the primary of the ignition. But I had discounted this symptom because the AFM/FP solution was easier to implement.

Meanwhile, the ECU I bought in the forum classifieds is wending it's way across the country to me so I may be able to do a replacement test with that, maybe even over the weekend. I'll try doing some multimeter tests at the ECU connectors before then.

Meanwhile I probably have to recharge my battery, and since I don't want to run an AC cord out the front I'll have to swap batteries with another car.

Probably I should remove my shunt to avoid flooding (don't need more problems!) since a function of the AFM is to cutoff the FP when no air is flowing and the engine isn't running.

With the shunt I can hear the FP and it always sounds the same, doesn't slow done and go tic-tic like some FPs I've known, so I assume it's constant displacement and excess fuel is recycled thru the return pipe to the tank. Not a bad implementation. The same system is used in hotels to provide instant hot water to all rooms: hot water constantly flows thru a circular system, unlike home hot water.

redfb

what do you mean when you say you can hear it running? I opened up my AFM flapper and it sounded like fuel or something was spraying

bliffle

I can hear a small motor running (with the key at ON, not yet to START) that I couldn't hear before. I infered that the new sound was the FP because I had shunted the test point. Also, it sounded rather like other fuel pumps I've known, except that it didn't slow down to a tic-tic as back pressure increased because the engine wasn't running.

Usually I can't hear an FP while the engine is running because of normal engine noise.

Since I already ordered a new ECU (for $45 I can afford to use it for a replacement test, in case the old one is blown) so I decided to check the voltages on the existing ECU and I dove under the passenger side dash ready to markup a print of the connections and WHOA! No ECU in sight! Just a big ventilation motor and a big old air conditioner! Probing around with my light I can't see anything that looks like an ECU. Even on the drivers side (I looked because that's the passenger side in Japan).

Am I going blind or is it somewhere else? I had heard that the ECU is under the seat or under the floor, but I supposed that was the 12A because now I was looking at the 13B specifically.

Do I have to drop the AC assembly to find the ECU?

Is it in a different place?

I feel so dumb. this is why I didn't attempt to answer the poll in the other forum about self evaluation as a mechanic.

redfb

no worries man i am an amateur mechanic myself here is a qoute from this:

https://www.rx7club.com/1st-gen-archive-71/electrical-se-error-code-write-up-285461/

"First, we will need to gain access to the ECU. The ECU is located under the passenger’s side floor. You will need to remove the scuff plate along the lower opening of the passenger’s side door as well as possibly the side panel that covers the passenger’s side front speaker in order to pull up the carpet. There will be a metal plate under the carpet the covers the ECU. This plate can be removed with a few 10mm nuts and bolts. Once this plate is removed, the ECU and related wiring can be seen."


did you see that scuff plate? It would be under that so the passenger doesn't step on it or the wires and mess it up.

bliffle

OK, I read that. I get it: the dern FSM posted an upside down picture (or something).

I got the 2 LEDs today so tonight I'll fab the tester for the ECU, per the instructions from GSL-SE addict.

redfb

sweet, thanks for the update bro..i feel bad because i haven't worked on mine to post any results...our new baby is keeping me rather busy

bliffle

That's OK. Enjoy these early years with your babies. It gets tougher soon enough.

I made the LED tester, tore up the floor, attached as directed, and all I get on the LED is the ON solid light at the start. No codes. Tried it again: no codes.

I tried to start the motor and it only ran about 1 second before cutting out.

Hmmm. I had high hopes for the ECU tester.

Before I close up the floor I guess I'll check the ECU itself for voltages, per the FSM.

Here's pix of the tester and the ECU and the test socket under the floor. I just crimped the LED leads into the male spade lugs. The LEDs were $1.99 each at Radio Shack and the leads come with 1/4" stripped at the ends so they're ready to go. I had spade lugs already, but RS also sells an assortment for $1.99.

cjf

iTrader: (1)

I have the same issues...seems kind of common with a few other rx7 owners on the forum .I brought my car to a mechanic...he threw up his hands and said take it outta here...he can't fix it.. I had to to the car towed to the shop for 50.00, then tow it back for 50.00....100.00 bucks out the window..


man this is annoying!!!

redfb

hmm..what is suppose to happen if you unplug your AFM? rx7dr. was saying something about that..

bliffle

Hang in there guys! There IS a methodical way to solve these problems and there IS an easy an economical way to fix them. We just have to move forward and have confidence in testing, measuring and logic.

The most important thing is to be clear and methodical. Write things down and report them here.


If you would rather have a mechanic fix it than DIY, you must first diagnose the problem accurately, then take the car in and tell him exactly what to do, for example, "replace the fuel pump and filter, change the oil, change the transmission fluid". That relieves him of diagnostic rsponsibility. It helps to have printouts of the affected areas from your FSM. I take them to Kinkos and have them blownup to 11x17, cropping the margins (I even do that for myself!). I always ask the mechanic ahead of time if he would like me to bring in the parts or whether he would rather source them himself.

I use sweeteners to encourage the poor mechanic, who is fearful of an unusual engine that may lead him to spending time and money that he can't recover, so you must diagnose and then venture the capital investment for the parts. I tell him he needn't hurry since I have another car, I throw in an oil change as a starter , and I also pay in cash. This is the way I trained my neighborhood mechanic in RX-7s. We've even done a transmission swap this way. Now he knows that 90% of the stuff on the RX-7 is plain old fashioned American car technology.

Unfortunately, I live in a different neighborhood now and I have little interest in training another mechanic, so I drive 15 miles back to the old neighborhood when I can plan in advance.

I'm in a situation similar to yours, except that I have a long history with RX-7s. But my 174k 85SE is parked at the curb with a similar no-start problem. I've done quite a bit of diagnosis already (in the week or so that it's been disabled) and eliminated a number of things (more or less) like the ignitors, plugs, fusible links, AFM (maybe). I also tested the ECU codes, which were NONE. So now I'll test the fuel pump pressure today at the topside of the engine preceding where fuel enters the rail near the Pulsation Damper. Ordinarily, I'd replace the fuel pump/filter myself, but I'll probably tow it One Block to "Ye Olde Village Motors" (as expensive as it sounds) because the SE is in front of the house instead of around back and I don't want to ghettoize the neighborhood. I'll talk to Ye Olde mechanic first and ask if he wants me to walk in the parts and what is he going to charge me, and I pay cash. He actually replaced a fuel pump on my 85GSL a couple years ago and charged me $200, which I thought was a little high.

That's if I finger the fuel pump/filter with todays test. If not, I'll proceed (patiently) with more tests and diagnosis.

Just pretend you're Dr. House on TV. The road to the correct diagnosis and the correct cure is not always straight nor is it smooth. Gotta use your brain. And when you're done you have to do a postmortem: why did I make so many diagnostic mistakes? Why did I start off on the wrong foot? Why did I make invalid assumptions? etc.

redfb

hey thanks for all the updates, the fuel pump was the first thing my wife's dad told me it had to be but, the guys at rx7.com told me it wasn't i guess i shouldn't have listened to them...i hope it means you have a bad fuel pump, i already have mine dropped out just haven't rebolted it yet so all i'd have to do is unplug it. I got my car to stay running longer yesterday by keeping it revved at 3k but as soon as i let off the gas it died. Normally it wouldn't even stay running no matter what, i am thinking maybe it's just going out gradually or something(the fuel pump)

cjf

iTrader: (1)

we all have the same problem...I replaced the gas in my tank ( I think it was old anyway) the fuel pump and the fuel filter.. no luck... The car just runs for a few minutes and if I even think about taking it for a spin, it konks out.. I have a parts GSL-SE and I have ben swapping things and still no luck..

I hope to have a rx7 friend/guru from this forum come down and help diagonois .. This is beyond me at this point ....and...apparently my mechanic who gave up...

If I ever fix it, I will let you all know...I hope it is not a bad apex seal or something.......shut my mouth!!!!!

bliffle

Have you checked the codes for the ECU? Gotta pull up the passenger side carpet and unbolt that footrest plate.

Does it keep running if you employ the fuelpump jumper in the black-hooded hanging connector near the air filter?

Did you check the Thermo Sensor behind the water pump?

If your car will run for a couple minutes then maybe it's the Thermo Sensor because it changes when it warms up. A new one cost me $20 at NAPA.

As they say, it can only be 3 things: compression, ignition or fuel. If it runs then it shouldn't be compression

So, did it keep running for a couple minutes with the new Fuel Pump or with the old one?

Do you have a timing light you can put on theplug wire to see if you're getting spark?

redfb

the old fuel pump and it ran for a few but i had to keep on the gas over 3k, i just went out there and messed around with the throttle a bit and got it to run but as soon as it went below 3k it was done no gassing it back to 3k because it'd die regardless..so you don't think it's the pump?

we have a timing light at a shop beside mine but, i would have to drive it there and it won't make it that far :/ does a fuel pump ever like cut on and off before it goes out or something? That's the only thing i can figure i know for a fact it's getting spark because we tested it for spark(and got the crap shocked out of my friend)

bliffle

Timing light is worthwhile for any DIY mechanic. They used to have passive neon lights for about $10 at every autostore: they're primitive but sometimes that's all you need. Electronic lights are about $70 but you can get them for about $30 at Harborfreight.

I've never had a fuel pump on any car be erratic before they fail, usually they just fail. But the symptoms may be changed if the filter is clogged.

Have you tried making that little test LED light and check the ECU readouts? All you need is the one LED for testing the ECU. If you have a failed Thermo Sensor the ECU will signal it with 3 short pulses close together. It'll also signal some other failures.

One thing I did that you might find useful is that I put my voltmeter on the primary of the trailing coil (and again on the leading coil) and started the engine and carefully observed (when the engine died) if the voltage died before or after the engine quit. That way I could tell if the ignition was the cause or the effect of the failure. In my case the volts dropped a split second after the quit, so I concluded that the ignition was an innocent victim: must be fuel.

cjf

iTrader: (1)

as for my car...I have an extra GSL-SE and I swapped out the ECU and hat was not it.. I have a new fuel pump and filter...that was not it,,,,I will look into the thermo sensor...

Bliffle---you sure seem to know what you are talking about...I will update here if I can fix my issue.....maybe it will help someone else.....darn I want to get this car running...

RXnos1200

iTrader: (24)

Seems like a vaccum leak if it runs when you're giving it gas and won't hold an idle when you stop.

redfb

well it does hold idle some days but others it won't i have tried to hunt down a leak but i can't find one...i am getting a multi meter tomorrow and making one of those homemade ecu checkers to see if i get a code

RXnos1200

iTrader: (24)

Have you checked compression yet? Check your plugs and see what kind of condition they're in.
SE gremlins all over the place.