Eng inj fuse repeatedly blowing on RX7
 

My 1988 RX7 (non-turbo) suddenly stalled and I could get it to start and may have flooded it in the process.

I tried de-flooding the car but still no start and just decided to check the fuse box.

The 40 amp "Eng Inj" fuse was blown. Got a replacement and tried to start the car.
It wouldn't and I checked the new fuse again. It's blown.

What would cause a repeated blowing of this fuse.

Thanks for the help.

Short circuit comes to mind, any wires which is laying to ground? Or is stripped/broken?

The INJ fuse powers the coils and the injectors. Does the fuse blow w/just key to on as you need to check this aspect. If it blows w/key to on then disconnect the coils and w/key to on does it blow again. If it doesn't then reconnect one of the coils and try the key to on and see if you can isolate the problem further.

After the fuse powers the coils the wire runs to the injectors. Before the wire reaches the injectors the wire runs through an Orange connector named FEM-02. FEM-02 mates the front and emission harness. If this connector is disconnected it will separate the coils from the injectors as powered by the INJ fuse. FEM-02 is located above and to the right of the ECU by the passenger kick panel. It is oriented in a vertical fashion not to be confused w/FEM-01, which is Orange as well, but positioned in a horizontal manner. If the connector is disconnected and the fuse does not blow w/either the key to on or start then you know the problem lies within the emission side of the harness, which is the part that feeds the injectors.

I didn't see this reply before I somehow got the fuse to stop blowing (so far) after I moved some wires around that go in back of the alternator and to the injectors.

I can turn the car over but it's not starting.
Maybe it's flooded but I did remove that Inj fuse and cranked over a few times before putting it back in.

Where do I go from here?

If your confident it's not flooded and the fuse is no longer blowing, then you might want to check continuity along the line set out above by satch.

You might want to check the 15 amp Engine fuse (interior fuse box). If either coil has voltage w/key to on at the B/Y wire then the Engine fuse is good to go.

I take B/Y wire means black/yellow (sorry just learning). Where can I find it and how do I test it or what voltage should be expected?

Leading coil has one White plug w/two wires and one is Black/Yellow and you would have to disconnect the plug to take a reading. W/key to on it should have 12 volts.

Thanks for the tips.

So far:

Engine fuse (15 W) is fine.
I get 12 volts from B/Y wire of lead coil (front of car).

Turns over but still won't start.

Afterwards, checked 40 W Inj fuse and it's fine.

Any further suggestions?

While your at it you might want to check the 30 amp COMP fuse and if the Black/White wire at the Green check connector near the leading coil (one w/four wires) has voltage w/key to on then the fuse must be good. If all that is good then you probably should try deflooding again. Sometimes the easist is not the most profficient. One method for deflooding is to disconnect the fuel pump and spray two seconds at most of starter fluid into the intake and try to start it and do that a couple of times and then reconnect the fuel pump and normally start the car.

Everything is OK so it looks like flooding at this point. There is a pump shut-off switch that was installed a while back. It turns the power off to the gas pump. Will that do?

Also with these fuel injection systems, how do I go about sticking in starter spray/fluid?

Thanks again.

Spray into the "air intake duct." Its the black plastic cowl on top of the radiator. And your fuel cut switch could also be in cutoff mode even when you have it in the on position.

Didn't quite understand this statement.
Are you saying to keep it in cutoff while I try starting with the starter fluid?

If it's working properly then you would have it in the off position when doing the starter spray trick. I was also mentioning the possibility that the switch is no good thus when you try to start the car and have it in he on position that it is still in the off position and not powering the pump. This explains "sometimes" why people have difficulty starting the car and it is because the damn switch is broken and getting in the way of things. Not saying this is your case but it is something to look in to.

OK.

So far I used over 2 cans of starter fluid. The car seems to only be turning over by running on the starter fluid since spraying more increases RPM. Pushing on the gas pedal appears not to make much of a difference. Also, LOTS of smoke, it hasn't dissipated with successive uses of starter fluid and it's also coming from the engine compartment. I'm guessing I might have blown a seal and/or the fuel pump isn't working ... but these are only amateur guesses.

Any further suggestions?

Thanks.

Disconnect the return fuel hose coming from the engine and place it in a jug. Then jumper the fuel check connector and w/key to on the jug should fill up w/gasoline. This would indicate the fuel circuit including the pump is working.

And using starter fluid should be used in only very small amounts and not copious amounts. It's just used to see if the car is getting spark which eliminates the possibilties of what the root cause is for not starting.

OK, my bad on the starter fluid.

What about all that smoke?

Anyway, i've attached two pics to make sure we are on the same page in terms of fuel lines (blue one) and the (yellow?) connector that needs jumping. Will try again tomorrow.

On a USDM engine the return line is closest to the firewall.

The fuel check connector is Yellow and found in a Black rubber shroud and it's located on the Emission harness which is the same harness that the Pressure Sensor is tied into. The check connector has a Black wire and a Brown wire and it's within a foot of the passenger strut tower.

I didn't have time today to look a lot but did notice something I didn't see yesterday.

There is big bundle of wires (harness?) that courses from one side of the engine, behind alternator, to the other side. The bundles wrapping is coming apart and looks burned. FYI two small wires from a connector into the alternator go into this bundle. Also I noticed that when turning the ignition key to on the temperature gauge goes past HOT on a cold engine.

If I have to pull that bundle of wires out to search for a short, is there instructions on this site how to do it or would be kind enough to provide them? Any other suggestions?

Thanks.

The twi wires connected to the back of the alternator are part of the Engine harness which has the least amount of wires relative to the other harnesses. You'll just have to pull apart the wrap and look for signs of damage. Pull up the wiring schematic and it identifies all the wires of the Engine harness. Found towards the very bottom of the wiring diagrams.

As far as the temperature gauge is concerned you might have a wire related to the gauge wiring grounded out which would cause the gauge needle to rise to the top of the range. The temp sender is located on the driver side of the engine below the oil filler pedestal and it's screwed into the side of the engine right next to the oil pressure sender which looks like a mushroom. It is rather small and has but one wire connected to it. The wire should be Yellow/White. The Y/W wire connects to a plug that is part of the Front harness and this wire is Yellow/Black. The mating of these two wires is found in an Orange connector called FEM-02 which is located above and to the right of the ECU/passenger kick panel. There are two of theses Orange connectors and the one you want to dial into would be the one which is oriented in a vertical position (up and down direction and not flat/horizontal). The top of the connector is the front harness side of the Orange connector and this is where the Y/W wire is to be found. Then on the bottom of the connector would be the Emission side of the connector where the Y/B wire will be found. You need to disconnect this Orange connector and do an ohm test to see if the Y/W wire is accidentally grounded or not. With the plug pulled from the temp sender and the Orange connector disconnected you then have access to both ends of this Y/W wire. W/the multimeter set to ohms (individual ohms and not thousands of ohms 1K) you place one meter lead on one end of the Y/W wire and the other meter lead on the other end of the Y/W wire and take the ohm reading and it should be a rather small number such as less than .5 ohms. This is to be done w/no key in the ignition. Again, no key. If this ohm reading checks out then you proceed to ohm out the Y/B wire that starts at the bottom part of the Orange connector and runs to the driver side under the dash near that kick panel to a connector called FME-01 which mates the Front harness to the Meter harness (part that goes to the gauge panel in the dash). The Y/B wire connects to a Yellow/White wire once again and this connector needs to be disconnected to do an ohm test on the Y/B wire that runs from the bottom part of the Orange connector (FEM-02) to FME-01. If you don't get a high ohm reading on the first test of the Y/W wire as explained you would then proceed to test the Y/B wire.

Actually the Y/W wire connected to the temp sender is part of the Emission harness and this wire is found on the bottom of FEM-02 and not the top part of the Front harness so the Y/B wire which mates w/the Y/W wire is found on the top part of the Orange connector named FEM-02. So the location of these two wires in FEM-02 were reversed when explained above.

Hi again Satch.

I tried the initial fuel pump/circuit check you suggested earlier. One problem was the "fuel check connector" you described doesn't seem to exist on my car. There was a black connector with two wires (black with yellow stripe & black with orange stripe) that go to the harness. The connector on this side is female with a T-configuration for the male prongs.

Next to this black connector is a white connector with two wires (black with yellow stripe & black with green stripe) going to the harness. The connector is male on this side with a T-configuration.

In either case, jumping these connectors w/key on does nothing in terms of fuel coming out of the return line.

What's next to check?

Thanks again.

If the wires don't match up you should not jumper the wires. I'm sure the connector exists as you just have to find it. Anyways, you can jumper the solid Black wire and the Brown wire at the Circuit Opening Relay to achieve the same thing. This relay is Yellow and Black and is found just under the dash and to the right of the steering wheel column. The relay plug has five wires total, two rows of wires, and the bottom row features the two wires to be jumpered (solid Black wire and Brown wire).

OK, I found it and it was well hidden.

Fuel is coming out of the return line at the place where this line/hose connects near the injectors. So looks like the pump is fine.

What's left to check?

did you ever check the wires behind the alternator to make sure that you weren't shorting out there?
It is common as it is the most confined place that thee harness goes through on the engine.

If you have fuel and spark then your engine needs to be deflooded "properly." To do this you need to disconnect the fuel pump. I wouldn't trust your fuel cut switch as it may not be working properly. After the pump has been unplugged you should spray "at most two seconds of starter spray into the air intake tubing" followed by trying to start the car (that's two seconds of starter spray at most). Then try to start the car. Now common sense dictates the car cannot start up and continously run because there is no fuel. If things work properly then the car should start up and die out after a couple of seconds. This helps burn off any of the excess fuel that might be contributing to your starting problem. Do this procedure two, maybe three times, and then reconnect the fuel pump and try to start the car in a normal sense. You can disable the fuel pump by unplugging the Circuit Opening Relay.

I'm glad you asked because I haven't and was wondering how to go about this in an efficient way.

Do I need to unwrap that bundle and then what points would I use to "dial in" to specific wires to check for breaks or shorts?

Also, how do I disable that Circuit Opening Relay? Just unplug all of it?

There is no relay involved. W/key to on the Black/White wire at the back of the alternator is supposed to have 12 volts and it can be checked while unplugged. The White/Black wire in the same two wire plug has 12 volts w/key to on and unplugged. The same wire has close to 0 volts w/key to on and the W/B wire plugged into the back of the alternator.

OK, found something.

First, I did the de-flooding technique then tried starting. No luck.

Next, I unplugged that white T-connector from the back of the alternator and checked the B/W wire. It reads close to 12 volts w/key on.

However, with that connector plugged back in, the B/W wire still reads about 12 volts w/key on.

It's supposed to. The W/B wire is the one that will have a different reading.

w/key on:

B/W wire (plugged or unplugged) about 12 volts.

W/B wire (unplugged) about 12 volts.

W/B wire (plugged) about 1.75 volts.

They respond just as they are supposed to so you know these two wires of the Engine harness are just fine. You might want to test for spark unless the car fires up briefly w/the shot of starter fluid. If it does briefly fire up then you need to check the condition of the spark plugs and see if they're wet or not as they should not be. You also might want to put a teaspoon of oil into the spark plug holes (lower ones) so as to help build compression.

Would putting in an engine oil additive from Lucas have caused a problem? I did this earlier the day that all this happened last week. I'll try the oil technique you suggested but was wondering if that additive is somehow interfering with any oil getting into the combustion chamber at all.

Here is the additive:

http://www.lucasoil.com/products/dis...tid=7&loc=show


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Bottom two plugs where wet.
I dried them and put a bit of oil inside chambers.
Still couldn't start the car.

Now what?

Thank you.

"Sometimes" wet plugs are damaged plugs and have to be replaced. Some people use a hair dryer in an attempt to dry them off to revive them.

OK, i'll repalce all four and see where that gets me.

Let you know what happens.

Thanks very much for the help and patience.

Satch, I replaced all four spark plugs and still can't get it to run. I get ignition with the starter fluid but as before it stalls once that burns off. Tried about 4-5 times this way without any signs of improvement.

Could coolant have gotten into the chamber because a seal went?

Anyway, what should I do next?

Thanks.

You might want to pull start the car in an effort to get it to start. Another thing you might want to do is remove the CAS and spin its wheel w/the key to on as this will cause the injectors to fire and you can hear them click if they are firing. If you were to do this you would want to disconnect the White two wire plug to the leading coil and the two electrical plugs housing the six wires to the trailing coil because they will fire as well and the sound might drown out the sound of the injectors clicking. Another thing you might want to check is pin 2I of the ECU as this is the Water Thermosensor which regualtes the amount of fuel when starting the car as it might be injecting too little perhaps. W/key to on this pin should read between 2 to 3 volts.

As far as the coolant is concerned did the wet spark plugs (old ones) smell sweet? If the new plug(s) were removed such as the trailing (upper ones) can you smell coolant?

And measure pins 3C and 3E at the ECU w/key to on and this will tell you if the injector plugs are connected/seated properly to the primary injectors. A proper reading would be 12 volts w/key to on at both of these ECU pins.

I have not tried push starting yet because I wanted to check readings on those areas you mentioned.

** The voltage a 2I is about 11 volts w/key on.



The voltages at 3C and 3E are about 11 volts w/key on.


If I did this right, it looks like 2I has associated problems with the Water Thermosensor. Where is it and how do I change/fix it? Could it be a short in the wire leading to it, if so then which wire?

Thanks.

I've never heard of pin 2I reading 11 volts w/key to on. Did you measure pin "3I" by accident?

I used this page for pin locations and measured the top 5th pin of the middle connector.

http://rx7.pw.cx/guides_manuals/coll...0ecu%20pinout/

Then that is the correct pin. Next thing to do is figuring why pin 2I reads 11 volts w/key to on. Try measuring pin 2A (same plug top row far right position and the wire is Brown w/possibly a White stripe. W/key to on this wire/pin should read 5 volts w/key to on. If this checks out okay then measure either of the Black wires in the smallest plug w/key to on and pin 3A and pin 3G should have close to zero volts as both of these wires are grounds. So pin 2A, 3A and 3G need to be measured w/key to on.

w/key on:

2A about 4.5 volts.

3A and 3G are 0.0 volts.

That's good news. So at the back of and the top of the water pump lies the Water Thermosensor. It should have a Green plug connected to it that looks much like an injector plug. Pull the plug off and see if either of the two pins in the plug are pulled back some and thus not making good contact w/the contacts of the sensor itself. Again, w/key to on pin 2I should measure 2 to 3 volts w/key to on on a cold engine. After messing w/the plug at the sensor recheck the voltage at pin 2I.

If it's the place I'm looking at then that sensor must have been missing for a while since that hole is empty and dirty. Here is a picture of where I'm looking, it's the top middle portion of the picture with wires sticking out:

http://mazdarx.narod.ru/manual/ROTAR...s/85813362.gif

Also, I found what looks to be a connector that is attached to a broken portion of some sensor. Maybe this is that water sensor. Here is a picture that looks like the connector, it's the green one on the right. The broken end looks a bit old as well, like it's not a fresh break but I maybe wrong.

http://t2.gstatic.com/images?q=tbn:A...ghn9_eF-gA2eEb

Have I found the right part?

In the first picture is a sensor for the electric fan on some models so that is not the Water Thermosensor. The sensor you need to find is located near the alternator and it's at the back of the water pump (screwed in) and in front of the engine. The connector in the second pic looks like the plug for it.

I just read this thread and I have to give you a huge pat on the back satch. If I finally get my car together and have any issues with wiring, you'll be my go to guy. Do you have this stuff memorized or are you just looking through the miserable Mazda diagrams? Either way mszlazak owes you a couple cases of beer for the time spent. Well done!

YES INDEED! Satch was terrific. Total patience with someone like me that virtually knows nothing about cars except for minor stuff.

Thanks again to satch.

OK satch it looks like I'll need to buy a part.

I did see that broken part but assumed it happened a long time ago because it looked like an old break ... apparently not.

I'll update as soon as I get it in.

Thanks again for all the help.