harley71105

Ok, I'm in need of some expert advice here because even the Mazda Dealer could not Diagnose. I know there is a lot of good free advice on this forum but if the moderators allow it I will gladly pay $50 to the first person that can help me resolve this dilemna.
I have an 88 GTU in very good condition. Occaisionally it will not start after its been running and sits for a little while. Engine turns over as normal, but is not flooding. Good compression. What is happening is that for short periods of time, no fuel is being dispensed through the injectors. New fuel pump. New fuel filters do not seem to make a difference. You never know when its going to do this, except that it wont in the mornings. Dealer replaced the hot start assist vacuum module and a relay to no avail, at my request to just try something.
Today, I noticed as I did the other day that when I take off the parking brake and let it roll as little as three inches, it starts right up because its getting fuel. Then runs great for a day or two, then I will shut it down, take care of some business, then get in and it will do it all over. HELP ?? This has been going on for TWO YEARS and I'm not kidding about the $50.
Thanks for any help.

1987RX7guy

iTrader: (3)

Rule one the DEALER does not know ****!!! Never go there!

Falcoms

not asking for the $50, but what it may be is you have a wire grounding out and that it may be that the coating is so thin that it only grounds out when hot. If this is the case, it would inadvertintly cut out the fuel pump relay all together until it is moved my a bump or wind moving over it.

Another idea, and this is VERY far fetched, is that if you turn the key, the fuel pump fires for about 3 seconds. What may be happening is that it is not getting power to the fuel pump module due to a poor ground, but when you roll forward, it may be bumping the connection just enough to get electricity to the fuel pump module. other then that, I have no idea

harley71105

Thanks, both sound good but I have even used the jumper to keep the pump running and it still does it...I like the ground idea...I've even regrounded some places but I'm thinking it may be the circuit that causes the injectors to open (electric) but the Mazda Dealer sort of ruled that one out....HELP....lol

WAYNE88N/A

2 guesses:
1) cold solder joints in ECU
2)dirty or corroded ground for injector harness, top of engine

harley71105

Thanks Wayne88. I like #2. I have two spare ECU's and both of them do the same thing. Ground for Injector Harness...now that sounds logical...at what point on top of engine is that located? or could I just ground the rail to say the firewall? So far you have the best running for the fifty bucks, dude...

WAYNE88N/A

located under the dynamic chamber, top of rear side housing (maybe rear rotor hsg?) usually under the bolt that secures the bracket on the "rat's nest" at that point...noticed when I changed my PD & fuel lines that's a really crappy place to have a ground- on top of a bracket that's sitting in the middle of all the oil/ dirt, etc...on top of the engine...I ran another ground to the firewall from that point, and made sure it made good contact with the harness ground terminal...

harley71105

Ok....tonight that is my project in the garage...sounds logical...if it does not do it again for 3-4 weeks...you made yourself fifty bucks dude....Hey, I'm from Tyler, Texas but been in Phoenix for a year after fifteen years in Shreveport, La...and I'm homesick for Texas with two 88 RX's...thanks

WAYNE88N/A

hey man, I'm not worried about the $50- just hope I'm helping you out- it could be a lot of things, ya know...maybe you'll get lucky and nail it...I've had 72 hour marathons troubleshooting the sh*t out of mine, too! (work on car,eat,work on car,sleep,work on car...you get the picture)

Digi7ech

iTrader: (1)

Your in Phoenix? Did you ever post in one of our threads? Bleh too many new ppl here now for me to remember.

You should meet up with us at the Pavillions some time.

The injector ground sounds pretty reasonable.
It's on the stud on the rear housing. 10mm I think maybe 12mm.

Most likely will have to remove UIM to get it though.

Zer0 Cylinder

if winner doesnt want $50, ill take it.

Terrh

iTrader: (7)

lol

if that injector ground is not on properly, **** won't work right, period.

I screwed it up on my car and it wouldn't start for ANYTHING. Take it off, clean it, and put it back on.. problem might be gone forever.

You'll probably have to pull the UIM and maybe the LIM to do this (just UIM on a TII, but I've never worked with an n/a so I dunno)

Icemark

Injector ground in a bogus answer... you might as well been a Mazda dealer mechanic say injector grounds...

Do you know where the injectors get their grounds??? Aparrently WAYNE88N/A, Terrh, Digi7ech do not...

THE INJECTORS GET THEIR GROUND FROM THE ECU

Okay now that we have proven most of the answers so far are about as on base as a Mazda dealer...

How do you know the injectors are not getting fuel??? Your simptoms are exactly like leaking injectors... not just like it, but exactly like a flooding situation.

Next time the car does this no start thing, hold the accell pedal all the way down without pumping it all while cranking.

Does the car start then??? If so, your injectors are dirty and you are flooding, as well as your Mazda dealer as proved his incompetence.

harley71105

OK...the way that I know no fuel is getting by is after several of these no start sessions, I would pull the plugs and man, they are dry as a bone...plus, I would have to do the after flood procedure if in fact it was flooding or it would not start. She runs fine when running but I'm telling you that no fuel is getting in during these episodes. When the engine floods it also makes a different cranking noise sounding as if it loses compression. This is different. I know she aint flooding and that is for sure...been driving rx's for 20 years and I know a flooded rotory when I have one. Of Course the ECU has grounds but so does other parts of the system...thanks for yur help too...

pip

I must admit mark sounds like hes got the right idea here, the symptoms are the symptoms for a flood. What do you have to do to get the car started again once it does the not starting thing?

Icemark

as far as injector control, ONLY THE ECU provides the ground control for opening or closing them.

There are no other grounds that have any effect on injector operation, than the ECU and it's grounds. So again, any ground to the intake manifold will have no change in operation of the injectors.

And yes way over flooded will result in a different cranking sound than regular starting. But only minor flooding will sound exactly like normal starting, just the car will not start. This is easily confused by most owners.

So, again back to waht I said earlier...

and if it does not, then what are the actual compression numbers???

WAYNE88N/A

hey Icemark- I call it an "injector ground" based on a couple of educated assumptions, since I haven't seen the schematic for the ECU internals...3 of the 4 grounds for the ECU go to that engine grounding point, number 24 of the '88 FSM (see pages 50-31 and 50-120)...the injector pins on the ECU are 3C,E,F, and H...the wires that the ECU uses for the engine ground are pins 2R, 3A, and 3G, same area on the ECU plug as the injectors, which leads me to believe they share the same PC board internally...I'm assuming the ECU is providing the switching functions for the injectors, in other words, the injector ground is not AT the ECU, or FROM the ECU, but THROUGH the ECU...have any circuit diagrams that show different? Please share them....again, for an '88...

WAYNE88N/A

BTW, you better have some pretty convincing proof since you had the nads to call me a mazda dealer mechanic...

Icemark

Damm newbies... always wanting me to prove something

Okay ECU grounds (wires directly hooked up to the ECU that go to ground-so in therory any ground switched to any device with path through the ECU and to these grounds) are:

Ground #6, 24

Ground #6 is grounded to the back side of the drivers shock tower, while ground #24 is the back top of the engine.

But either ground will supply ground to the ECU for running purposes as they are tied together on the circuit boards on the S4 ECUs.

Parastie

I completely agree with Icemark. I assume you're referring to the ground that goes to the injectors and to a cheap plug on the firewall correct? I have that ground completely removed in my car and it runs without a problem.

HAILERS

I don't agree with Icemark. The grounds for the ECU (and the injectors) are on top of the engine. ground point 24. Ground point six is not a player. Look at your schematics and show me where six is involved. I'm sceptical about ground point six. IF you take that whole gang of grounds off JC-01, of which 6 is one of five ground wires at JC-01, then the car won't start because the Main Relay won't pull in.

Better watch it, I'm the type that'll depin the wires at the ECU that go to ground point 24 and try to start the car.

An engine will not start without the grounds at ground point 24 attached OR some homemade grounds to the wires b/t the ECU and ground point 24.

And I don't think it's been proven this car is not getting fuel. I don't understand the *let the car roll three feet and it starts* phrase. Downhill and pop the clutch???

And I'm getting my ground info from the 87FSM.

WAYNE88N/A

good idea, HAILERS, the only way to settle this is to disconnect ground point #24 on the engine, and see if the car runs...I gotta use mine to go to work in 2 hours, so anybody else want to "play" with theirs? Also offended by the "newbie" remark, Icemark...If you're calling a guy that's had rotaries since 1989, been an aircraft electrician since 1985, A & P mechanic since 1989, and FAA certified aircraft maintenance & powerplant inspector since 1994 a newbie, you must have some pretty outstanding qualifications yourself...

ZenEfini

HAILERS

The ground points on a series four are in this jpg: http://www.teamfc3s.org/forum/showth...threadid=28563

The individual ground wires and what they go to are found on the schematics in the fsm.

harley71105

I really appreciate you guys keeping this thing going...all of you are doing a great job and I am learning just by reading your post's....rolling the car is simply just moving it... no clutching at all...and when I refer to no fuel I mean there is pressure on the rails But evidently it is not getting past the injectors and then all of a sudden perhaps on the next crank try it will start up completely normal, no smoke, no rough idle, she runs fine. By the way, the only "mod I have done" is to change out a leakey thermostat housing, the part where the temp sensor is located that signals the cooling fan (stock). The replacement neck from the dealer did NOT have a threaded hole for the sensor so my electrical connect is just sitting there disconnected and could this be causing some conflicting electrical signals in the system that manifests itself by, in this case, not allowing injectors to open only intermittently at start up?....and that other ground by the dynamic
chamber on the back top of the engine is that one of these that you are referring to? It was disconnected but even after re-connecting it still has the intermittent problem, but doesn't seem to be as often...
Sorry about the long post but this is quite a challenge...and thanks again, men....