Will not rev past 3k with out turning key to start
 

Ok so I have been chasing a problem with my car.
I have swapped the engine and alsorts of stuff but I think this is just miata stuff.
So the car starts but when I go to rev it it will not rev past 3.5k there is clicking noise under the dash which is the fuel pump relay but it is not stopping for no fuel the car is not seeing rpm's so it does not spark till its back under 3k.

Now here is the funny part if it twist the key to start it will rev all the way. I only did this a few time for worry of my starter but it sure is true.

I got under the dash and the yellow and black denso relay attached behind/on the steering colum is clicking when it hits the 3k and the tach zeroes out but I believe that is the fuel pump relay could it being bad cause this?

Or is it something with the ignition key switch.

It's a fuel related issue. When you turn the key to start, it jumps the FP relay and blips the fuel pump (since the stock car relies on airflow to run the fuel pump).

why would the tach on the dash and the Tunerstudio go to 0 much quicker than the actual engine and why does the o2 not show lean.
A fuel pump relay is 90 bucks. Not cheap.

Here is a log I thought it was the Cas triple checked the extended wire and swapped it with a working spare same exact thing 3k then it dies. I thought about buying another till I noticed how much it reved with start switched on.

Jumper your fuel pump and see if that fixes the problem.

Thanks for your help Savington I really appreciate it.
So are you saying I jump something inside the diypnp or inside the relay?
If inside the diypnp could you please be more specific what do I jump to what.
12+ to fuel pump pin or something

Jump FP to GND in the diagnostic box.

Sounds like he doesn't know about the box.

Raise the hood, and look around the area of the driver's side shock tower. You will find a little black plastic box, about 1.5" square. Flip the lid off the top and you'll see a bunch of terminals, and a printed legend on the lid.

Locate the two terminals labeled FP and GND, and stick a jumper wire between them. You'll know you've got it when you can hear the fuel pump running with the key on but the engine not turning. Be careful in there- you can blow shit up if you jumper the wrong wires.

Start the engine and see if the problem has gone away.

FWIW, the relay itself is almost certainly working fine, presupposing that you're right about this being strictly RPM-related.

well this is the wierdest thing. I loaded an old tune and it was working but the tps was not set right so I used the tps calibrater and then it died and now will start but not run and it is very lean now. So I will check presure tomorrow and replace relay if needed.
Just makes no sense something in the diypnp is not controling the pump right maybe?

Fuel pressure is there. I sucessfuly tested the fuel pump with the jumper. The pump real burdens when I squeze the return with pliers.
I will reload firmware and see if that gets the injectors firing in the morning.

What all did you change since the car ran well last time? Did you change the crank and cam trigger setup? I had a similar issue when I went to a 01+ setup from a 90. The issue was the polarity of the "Ignition Input Capture". I had to flip it and the car started to run smoothly and rev good.

OK same as before will start but the second you disengage starter it dies.
Rev with starter engaged it revs.

But was the Fuel Pump jumper still in place?

Yes the jumper was in. I specificly tried it that way to take it out of thing that could be causing this.
Does the diypnp even know I am turning the key to start. It is my understand that the computer knows I am cranking because the rpm is below what I set 350rmp for me.
Anyway all the same leave the starter engaged and the car runs all the way to 7k.

the MS knows you're cranking if your RPM is between 1 and the number you have set as the cranking RPM.

unsure how the starter can be engaged and you can rev to 7K...doesn't that cause "awful death noise"?

is it maybe possible your ign. switch is not switching power correctly?

Brain that is what I am thinking its the only thing that makes sense is the key ignition is bad or something.

Wait I missed redriders comment so you are saying change ingition input caputre in Ignition options tab to falling edge?
Is there any chance this will hurt anything?

Just as an FYI, the reason we were telling you to jumper the FP relay:

On the 90-93 cars, the FP relay is normally driven by a mechanical switch closure inside the AFM, not by the ECU. This switch closes whenever any airfllow at all is moving through the sensor. But during cranking, there is no (or very little airflow), so these cars also were equipped with a wire leading directly from the starter circuit to the FP relay, causing the relay to close whenever the starter is turning.

Now, in the MSPnP configuration we assume you have removed the AFM, and the MS is driving the fuel pump relay directly. (DIY did a neat hack to make this possible, and it's this hack which requires that the ST SIG fuse be removed on all '90-'93 cars running an MSPnP or DIYPnP.)

The theory was that the MS was, for some reason, shutting off the fuel pump. Given that you describe this problem as being RPM-sensitive, and ALSO cured by turning the key to start, it's still the only logic explanation I can think of. (RPM sensitive points to the ECU in general, and fixing it by turning the key to start suggests the fuel pump, as this would be driven by the starter circuit.)


However, I just double-checked the wiring diagrams for the '90-'93 Miata, and the location of the ST SIG fuse is such that its removal would break the path between the starter circuit and the fuel pump relay.

Which leads me to ask: You DID remove this fuse before ever operating the MS in the car, correct?

Yes the fuse is missing for sure. I had a buddy helping me with the car and he kept saying I needed a fuse there.
Thanks for your help with this guys.

I figure either the starter engage forces the ground to be solid or the key ignition is messed up. I found a link to a cleaning guide I am going to try tonight:
Cleaning the Ignition Switch (1990)

My question is when it was doing the 3k limit earlier it was the fuel pump relay that was clicking when it hit 3k so is it possible I am getting a intermiten power problem to diypnp or inside it?

That's where I'd start.

if you could hear the relay click at 3K, it's probably shorting... I'm sure if you logged the event (which you should) you'll see the ECU losing power/sync.

could it have anything to do with netrual switch or any off the wire to the trans?
Here are some logs of it happening
on the second one I had the fuel pump jumped. I am thinking it has to be ground related. I am cleaning inginition switch and no impovement I am now looking at wiring diagrams for a test process.

OK so in using a multi meter on the key and reading the manual it looks like ign2 loses power when starting. I have more logs where I hold the key in start pos far enough to keep running but not enough to engage starter it revs but will not idle. You can see the rpm in the log drop to 0 from 6k in a milisecond then jump up a couple times as it dies when i let the key go back to run.
Are the ign1 and ing2 in the MS these same ig1 and ig2 labeled on the keyed ingintion switch because neither says it is connected with an ohm meter.
I am completely stumped.

No. You'll blow your coilpack if you try to connect them.

See 19.34.33 record 494 3600rpm record 495 1rpm

What does ign2 on the ingition switch go too? Does it go to the diypnp at all or does it just see power on.

http://www.miataforumz.com/1990-200-...ing/92diag.pdf

page 5.

All the stuff that shuts off when the starter is engaged and which isn't powered when the key is in the ACC position. Basically the HVAC system, the rear defroster, the power window motors, the windshield wipers, etc.

In other words, it's supposed to be "dead' when they key is in the START position.

Ok what next, you are right ign2 goes to nothing I need thanks for the diagram I was looking at the more complicated one in my manual.

I just dont know. What does the neutral switch do maybe it messed up I was tightening the pfr think.

To be honest, I'm still not certain that I understand what you are describing. If the fuel pump does in fact shut off when the RPMs exceed some exact point, then you have a software configuration problem in the ECU, plain and simple. My very first step would be to save an MSQ of your current config, and then load a known-good default and take it for a test run.



In the stock system, it sends a signal to the ECU (in parallel with the upper clutch switch) that the transmission is in neutral. This flips a bit in the code which disables over-run fuel cutoff. It also goes to the cruise control module (if present) to disable cruise control any time the transmission is in neutral.

With the DIYPnP (or any MS), the neutral switch is connected to absolutely nothing unless you have built and configured launch control.

Recheck all your wiring

Joe your right let me tell you what its doing now.
The fuel pump is not shutting off. Some one suggested the fuel pump but it is not that with the jumper I can hear it run the whole time and the car dies the second the key hits the run position.

The car current does not idle or run at all with the key in the run. The car dies and the rpms on the gauge and TS go to 0.

The problem is that something is changing a major portion of the car to off when its actually in run. The diypnp never loss sync and the logs I posted show the change in rpm (in the log mentioned above the car changes from 3600rpm to 1rpm in one frame.This is not what the engine is actually doing but something about the ignition key( which I checked out per the manual with an ohm meter) is turning of a main system.

The few times it has run since this started a week ago it cycles the fuel pump which I hear from the relay ( i replaced with new no change) which tells me the ecu or something thinks I am turning the car off.

Basicly when I turn the key to the run position from the start position it is the same thing happen as if you turn the car off all of a sudden if it reving in neutral at 7k. The tach goes to 0 much quicker than the engine.
and when you turn it back on if the engine is still turning fast enough if fires back up as the fuel pump primes like everyother time you turn the car on.

Oh and I confirmed I have 12v in run at: igniter, cas, coils and injectors(the diypnp is still logging so its running).

Is there another like a sensor ground that could be going bad or something. I just dont know what to check next.

I am still confounded by what I'm reading here.

Simple question: If you put the stock ECU back in, does the car run properly?

No it does not. I tried but I have a vtps and no maf.
I am sorry I am not explaining it well
So imagine the key has 5 position
1 off
2 accesory
3 run
4 start but not twisted far enough to engage starter
5 and twisted far enough to engage starter.
The car runs and can data log in only 4 and 5 when i let the key return to 3 run the car died and tach on dash and TS go to 0. It also data logos and diypnp has power in 3.
But if I hold it in position 4 it will rev and even idle if i let of the throttle really slow(I have not tuned any of the idle reloaded 1.6 460cc msq as I am running stock cas,coil and igniter.

This car ran after the engine swap with no changes from the current set up for 2 weeks. No problems ( It back fired a little and was not perfect needed auto tune time).
I changed radiator and screwed the stock gauge temp sensor into the engine and adjusted and welded the downpipe up.
I did not do anything I can think that would cause this.

Well I checked the ignition switch and if you disconnect ign2 it will not even try and start.
I verifed that ign2 is the only thing that is changing. Something ignition 2 is hooked to is messed up. It has to be relay. What relay are between the ign and the cas,coil and inj?

when you are referring to ign2, are you talking about on the ignition switch itself?

if you are, pull the fuses one by one on it, and try. (wiper, heater, air bag, power wind, cigar)


im goign out on a limb and saying i bet cigar is the issue... but that's a complete wild guess.

The "Main Relay" uses IG1 to drive its coil, and that switches power directly from the "INJ" fuse to 90% of the engine electronics. (ECU, CAS, injectors, sensors, etc.)

The ignition coils are supplied directly from the IG1 terminal with no relays and no fuse other than the "Main" fuse.

It's all in that file Brainey linked to earlier.

Oh yeah sucess. Pulled the wiper fuse and she starts right up.

So major issue resolved but how do I figure out what is going on with the wipers?
Pulled plug at motor and fuse stll killed car.

you really hate that diagram i gave you dont you?


it shows you exactly what's on that fuse: basically anything that's a BLUE wire.


I doubt it's the heater control unit, as that's just power for the light bulb.

so things you can try unplugging one at a time:

a/c relay
wiper switch
wiper motor
abs module (under steering column)
airbag control module

Brain you where so right thanks for the idea and the diagram.
It was removing the wiper fuse in the top right corner on the underdash fuse box that did the trick.
Joe thank you for your help too. Its nice to have experts with experience to lean on.

I hope this post help some other person with a similiar problem down the road because the road from the symptoms to the solution was a long one.