So I go to start my car in the morning after driving it yesterday and it turns over but won't start. After various investigations I have learned that I'm getting spark on all plugs, and that my Fuel Pump works but is getting no power.

From the time I've owned it, the car has always had a fuel cutoff switch, and it's always run the pump whenever the ignition is on. I've confirmed that the switch is on the main power wire between a relay near the ECU (NOT under the driver's side by the steering column like I've read about here, why is that?) and the actual fuel pump. That relay is a 5 pin (again, not 6 like seems to be the norm here) connector that also connects with the Air Flow Meter according to the Haynes wiring diagram.

If I ground out the AFM connection to the relay, with the ignition on, the pump will start. I guess the main question is what has recently failed on my car? The relay or the AFM? How can I test the two to know for sure?

The other thing I'm wondering, is why has my pump always run with the ignition on, if the connection to the AFM is supposed to prevent it from running? Maybe my AFM was already broken and now the relay too?

Would appreciate any advice or input. Thanks guys.

 

I'm sure doc will chime in, he's more up on this than I am. When starting an SE, the relay powers the pump when the ignition is in the crank position. Once the engine fires, the afm door opens and holds the pump circuit open when then the ignition returns to run.

 

Oooohhh, ok trochoid. That does make sense then, and also explains why there's a "From Ignition 'START'" line going into the relay in addition to the regular ignition line that comes alive with the key in the 'on' position. So it would seem that my relay is indeed bad as it doesn't react to the 'Start' circuit. I'll test this out when I get home just to make sure that it's not a wiring problem on that Start circuit.

Thanks so much for the help!

 

I have heard of alot of guys with Se's that have installed the fuel pump switch because they were having trouble with flooding. (leaky injectors). so they would
cut off fuel to the motor before they shut it off to prevent the saturated fuel from being there when they restarted the car. Also have seen this because of failure of the AFM, Allowing the signal to go to the fuel pump and turn it on before starting. This can be caused by a sticking or bent flap door. Usually the bent door is from a large backfire.

Now the fuel pump circuit also goes thru the trailing ignitor as does all 84-85 Rx7's. I have yet to come across a bad fuel pump relay though.

 

My Tach bounces as the car turns over. I figured that rules out the trailing ignitor??? Also there's the ground thing with the AFM circuit which causes the relay to switch and activate the pump. I suppose there's a first time for everything. Who knows, maybe the manual switch puts undue stress on the relay everytime it starts up.

Makes sense about the reasons for the manual switch in the first place. Thanks for the input Doc!

 

New update: Using the AFM side of the relay I jumped the test connector to have the pump run just with ignition, except I also have control with that manual switch. Anyways, it still didn't start. <cry>

I checked spark just by grounding the plug boot to the strut tower so unless all 4 plugs are shot I'm getting spark just fine on both leading and trailing. Also by the time I quit trying it definately smelled flooded out of the tail pipe so I'm sure there's fuel getting through. But it doesn't even really threaten to start, just turns over with no life.

There also is a pretty loud clicking sound coming from the engine bay as it turns over. Since it's only me I can tell exactly where from, and also I'm not even sure it hasn't always been there.

I fear for the worst. Any suggestions guys?

 

Pull the plugs, clean them and deflood the motor. It will not start flooded. You could try (before deflooding) disconnecting power to the pump then put your foot all the way down to the floor and see if she will clear her self out and start.

 

New update.

That clicking sound is just the AFM flap as it opens and closes from the air flow when its turning over.

Here's the situation. The Fuel Pump has been ruled out as a culprit. The car has spark on all 4 plugs, has fuel (flooded it twice), seems to have good compression and cycles air quite well out the tail pipe, but will not fire at all. When turning over it just continues to crank, I don't think I heard one single solid detonation. Since I also have the pump on a switch I can crank for extended periods of time with no fuel. Even after deflooding and a lengthy non-fuel duration, it won't even fire in a transition period after I turn the fuel pump on. And since the plugs get wet, there's certainly gas there too.

The tank of gas was down to 1/4 when I parked. Couldn't be a bunch of water cuz I coudnt have driven it home.

The only problem I've found was the intake air temperature sensor is broken and thus not connected. Could that one sensor prevent it from at least firing a few times and trying to start? It just turns over completely dead...

 

Yes, one of the temp sensors will cause a no start. Doc called me on this one one day, lol. I'm not sure which sensor it is though. I know there is one in the intake, the rear of the waterpump housing, the bottom of the oil pan and the bottom of the radiator. My best guess is it would be on of the 2 upper ones. If it turns out to be the intake one, I have used an S4 sensor in place of a broken SE one before.

If your plugs are wet, they will not fire, keep cleaning them.

 

The only sensor that will cause the Se not to start is the Coolant temp sensor for the ECU that is located in the back of the water pump housing. And only if it is unplugged.

You need to pull the plugs and crank the motor over to blow out the rest of the fuel. Squirt in some motor oil in the spark plug holes(to increase cranking compression). Put in some fresh plugs. Get another vehicle and hook up jumper cables to the Se or if you have a battery charger with the booster function on it then you can use it. Start cranking, if it seems like it is going to flood again, depress the gas pedal about half way and hold it there. I have had Se's that took alot to get restarted after a flood situation. It will restart its just a matter of keeping at it and making sure that there is lots of cranking power to keep the motor spinning.

 

Well I can say that the plugs aren't great anyways, so I think it's worth trying for sure. On the two floods I mentioned, I did pull the plugs and spray the fuel out then too, but I didn't try the oil thing. I have a charger and a dry cell so I have a pretty good charge reserve in the morning. I'll give it a try, and I'll verify the collant sensor too. Thanks again Doc.

 

well first off, I can tell you that your AFM is VERY touchy..so if there's ANY kind of an air leak after it (incl. but not limited to intake hose, Bypass Air Control Valve, upper intake gasket, lower intake gasket) it wont read correctly and wont start...I fought this when I upgraded to the S4 intake....screwed with me for 4 months..I felt stupid afterwards.

Second, install a manual fuel cut swtich! Its soooooooo much easier than pulling your plugs..Trust me..I have one.

Third...do me a favor and swtich the leading and trailing ignitors. Not the connections. Physically move them. It worked for me also when I had the no start issue. Call it stupid but anything is a try for you right now.

Fourth, http://www.wankel.net/~krwright/files/manuals/1985_RX7_FSM/85RX7(4B)Fuel&emissions_13B.pdf
is a link to the Factory Service Manual that shows step by step of how to test your AFM...actually the whole FSM is there to test anything else you want.

Good Luck.

 

Thanks for the advice blazer. I certainly think I'll have to go step-by-step and verify one component at a time at this point. I do have a manual fuel cut switch, yet it still will not fire, even for a brief moment after I turn it on. I know all 4 plugs are sparking for sure, cuz I've verified with each of them out of the block. Was there another reason you were thinking to move the ignitors?

I tried it again after blowing the vapour out and still no go. But I haven't been able to get new plugs yet, as the dealers no longer stock them and require an order to bring them in.

 

lol..i work at a mazda dealership and you're right...they dont stock crap..and all the prices are really expensive. If I didnt' get my discount, I'd shop at mazdatrix.com except for the AFM where I found at advanceautoparts.com for $279 + $69 core for a Python Inc. AFM

No real reasoning about switching the ignitors. Just that before the small intake air leak that messed me up I had a cituation with no signal sent to the injectors..but if you're flooding the engine then that wouldn't be a problem.

At this point I'm calling your situation bad AFM or intake leak after AFM...

Some background also is helpful for us too...how did you get to this point? Did you buy the car like this or did it suddenly one day not start?

 

^ You might want to go back and read what he originally posted,lol.

 

drrrrrrrpp....here's my sign...

 

????

Yeah, I realize that some of my first post was a bit wrong because I was on the wrong track with my fuel pump....

Anyways, I've driven the car as a daily driver for 3 years with no running trouble at all. My tranny packed it in and my heater core broke but it's always run very well. It was rebuilt not long before I got it, and I've driven it about 25K miles since I got it.

Right now I'm waiting on plugs and that sensor, and I'll also snag a new cap and rotor, and change out the fuel filter too. I'm off to buy a multi-meter and I'll just go through the FSM, starting with the AFM and collant temp sensor (which is indeed plugged in, btw).

One thing I'm wondering is how I could check my fuel/air mix to help diagnose the cause of the problem?

 

Wideband O2 sensor in place of the stock one.

 

I've never used them. Wouldnt the fuel need to be burning for one of those to work???

 

Engine needs to be running, yes.

 

I am racking my brain trying to ascertain what I'm missing out of this picture.
Being that nothing was touched prior to the car running perfectly the day before.


If you have a mini-torch you could spray the plugs down with brake cleaner and heat them up. You can still do this with holding onto them with pliers and heating the end up with your gas stove if you have one.

Just for the heck of it. Need you to check the engine fuse in the fuse panel and the 2 fusable links that are on the top(closest) juction box in the engine bay. You can switch the links with the headlamp ones for test purposes.

If the air intake hose has separated where it joins in the middle it would cause it not to start also. I'm reaching but I believe these things need to be looked at.

 

yes....more diagnosis before replacing parts

 

Felgar, what is going on with your car? It is driving me nuts,lol. Updates please.

 

Hey Doc, sorry for not posting back. I have very little new news. I did verify the engine fuse in the interior but didn't even verify the fusible links yet (but they look fine visually). I'm waiting on the Air Temp Sensor from a supplier here in Calgary and I'll be picking up the new plugs, cap, rotor, etc from them as well.

I was going to pick up a multi-meter and start verifying the AFM but I've been so busy with other things that I haven't started that yet. And then I came home yesterday and the battery charger I was using reported "charge error" and my battery was stone dead. So I had to spend last night charging back up. I might be able to verify the fusible links tonight, but even if not, I'll report back as soon as I get back to work on it.

Thanks for keeping it in mind though Doc; I really appreciate it.

One thing I've learned is that the RX is no longer a suitable daily driver. Parts are just too hard to get now which makes fixing problems take far too long. But I'll be hard-pressed to find a car that I enjoy driving as much as the SE for less than about 10K, so I don't what to do. Maybe a BMW 323 or 325 from 94-98...

 

I've never owned a daily that wasn't a 1st gen. I'm very impressed that you even found a place that sold an Air Temp sensor, though it just controls one of the solenoids for the EMISSIONS ONLY if its the one in the back of the intake plenum....I found that out later. There's a second Air Temp sensor located inside the AFM that is used to richen or lean the air/fuel ratio. Air temp sensor wont cause a no start that I've ever heard.

I'm still putting money on intake leak after AFM..only because the day before, it ran great.