cumberlandrx7

I just finished my TII swap into my 1990 rx7 and am trying to start it up but running into a problem. I installed a walbro 255 fuel pump and when I turn the key to aux position it doesn't prime or send fuel down the lines but when I turn the engine over it sends fuel down the fuel line (i tested this with the hoses off to make sure) I am able to start the car up and it runs for maybe 4 seconds but when I stop turning the key to the start position and put it back in the aux position the fuel stops running and it dies. Any ideas as to what it could be??? a relay maybe??? if so where is the relay??

RotaryRocket88

iTrader: (7)

If the engine is not running, the fuel pump will not run in the 'ON' position. The flapper door in the AFM must be open to trigger the fuel pump switch, or the yellow test connector on the passenger shock tower must be jumpered to get it to run. If it starts then dies, the new turbo AFM may be bad. Test the fuel cut switch per the FSM.

Turbo II Rotor

iTrader: (2)

My car did the same thing and it was a bad relay connection under the dash.

HAILERS

Why don't you jumper the yellow two socket fuel pump check connector and put the key to ON. You should be able to hear the pump run and fuel pass thru the rails. If not, then there is a miswire somewhere.

Then try to start the engine and see if the engine keeps running or not. I mean to say that the pump should now run all the time the key is ON.

Sure the elect plug is on the AFM?

cumberlandrx7

Ok well I checked the main relay and it is fine, and the fuel pump shouldn't run when it's "ON" but it should prime and send some fuel down the lines but it wasn't. The AFM's seem to be fine, I didn't test the fuel cut switch but I did put a jumper on the yellow test connector and after when I turned it to the aux position the pump was priming. Another concern of mine is that I bought engine and it was clear the previous owner had it set up to boost high but it didn't have the N370 ecu on it... it had the N3A7 ecu which i beleive is the 3rd gen ecu. Any other ideas besides the fuel cut switch before I go and buy a new ecu, they can be kinda pricey those ecu's.

cumberlandrx7

hailers: sorry I didn't refresh the page before reading your post. I jumped it and it primed constantly so i think the wiring is fine and I was able to hear the pump unlike before. I tried to start the engine afterwards and it still just dies out after about 3 sec of running. Also the AFM is plugged in

HAILERS

NOt much help from here. You know it's not a fuel delivery problem now since the pump runs all the time with the jumper. Sounds a bit like a Large air leak of some kind. Has the traits of that.

There's been a lot of problems with JDM engines going into USA cars in the fuel arena. The JDM fuel hoses are connected to the engine just the opposite of what our cars are i.e. the return line will be the pressure line and vice versa.

So the pump may run, but the fuel isn't going anywhere. The fuel should run thru the rails continuously and dump back into the fuel tank. Listen for the fuel passing thru the rails. Or maybe just swap the fuel lines at the engine and try again. IF it does not work, put 'em back where they were.

OR pull the return line off the engine and with jumper in and key to ON, fuel should flow from the engine side continuously. Maybe put a spare piece of hose on the hard line on the engine and the other end in a bucket or???? so it does not flood the floor and catch fire.

Banzai-Racing

iTrader: (11)

Are you using the same harness that the PO was using? If the engine ran with the FD ecu then there are a bunch of wires that were changed on the engine harness, several that would effect fuel supply.

For instance pin 1T on the FD ECU is 3K on the S5, this controls the circuit opening relay, which is responsible for the fuel pump priming and running.

Look at your harness at the ECU, does it look like any wires have been swapped?

cumberlandrx7

It is completely possible the lines are on backwards, I've taken them off and the fuel does run out them and also I did flip them from what they were on the N/A engine. As for the harness, no I am using the N/A harness because it is easier to swap a TII in using the N/A harness but it doesn't look like the jdm harness was changed in any way.

cumberlandrx7

Also I beleive I read somewhere that people who had faulty N374 ecu's were able to use the N/A ecu to start the car up, I tried the N/A ecu and no luck either, any ideas??

cumberlandrx7

Ok after looking at the old harness that came with the engine I noticed that the p.o. may have swapped some wires and there are signs of soldering (i.e. taped wires near the ecu plug end of the harness)

Banzai-Racing

iTrader: (11)

It doesn't matter, you are not using that harness and you are not trying to use the FD ECU.

Did your car ever run as a N/A? or did you buy it non-running?

Check all your grounds.

cumberlandrx7

ya it ran as an N/A

cumberlandrx7

Ok so now I am following a new path... I started from where the problem was, the fuel pump would not hold power after I released the key once the car was started. I checked back at the pump to see if all the wires were proper, and they are good. Then I moved to the relay located under the steering column (I beleive the main circuit opening relay??? it's the black and yellow relay with 5 pins) anyways, I took it apart and opened it because I noticed I wasn't getting proper resistance readings. It turns out that one of the coils (there are 2 coils inside) like I was saying, one of the coils had a break in the coil but luckily it was only 1 wire but others seemed to be slightly damaged in the area but not broken. I fixed the 2 ends together and tested it just on the battery to see if after the first coil opened up if it held it open with the other coil and PASS it worked, also the resistance was showing better values. I plugged it back into the car and had a pass/fail bulb hooked up to the fuel pump so I could see when it was getting power. I turned the key to the "ON" position and the light turned on for 1 second about and went off (I thought this was the priming so I thought it was working). Well I heard the relay click not once or twice but three times and it seemed odd that it would do that so I tried to start up the car and it started then died right after, I tried again but this time when I turned the key to the "ON" position the light I had for the pump did not turn on. I think something is causing the relay to mess up, i'm not an electrical engineer but what could be causing this? i'm afraid that if I get a new relay it will just get fried like this one.

Any help at all would be great i'm running out of ideas.

cumberlandrx7

here seems to be a similar thread that never got answered... has anyone ever fixed this issue ever?? lol

https://www.rx7club.com/new-member-rx-7-technical-256/fc-rx7-no-power-fuel-pump-faulty-relay-pics-included-786591/

Banzai-Racing

iTrader: (11)

Relay under the dash is the Circuit Opening Relay. Ground pin 3K at the ECU and see if the fuel pump primes. Honestly it sonds like you have not bothered to check your engine harness gounds. If the ECU is not grounded properly, it is not going to function correctly.

cumberlandrx7

Ok I was mistaken, it didn't fry the second time... it still works.

I've been tracing grounds all day, and there isn't an easier way lol. I took alot of care when installing the harness and engine to make sure all grounds and wires in general were properly done but who knows maybe I missed something.

Now what I am noticing is that somtimes (not always) when I turn the key to "ON" I hear the relay under the dash and some relay in the engine bay click and the light hooked up to my pump lights up for a second then goes out, is it priming correctly?? perhaps now my problem is something else?

I will try that right now banzai, thanks for your help btw and everyone else too.

Not sure if this matters but when I turn the key to the "OFF" position I have the "OVERHEAT EXH SYSTEM" light on. Is this a faulty O2 sensor or what could this be?? and does it have anything to do with my issues??

cumberlandrx7

I built a block off plate for the bypass tube/hose thing that went to the stock catalytic converter and maybe this is the issue??? I'm not sure how to test it or fix it from here though. If it's irrelevant then i'll worry about fixing that after the car starts lol.

HAILERS

You should not get a light if the key is truly to OFF. Do you have that light when the key is out of the ignition?

On a NORMAL car that light indicates the temperature switch under the passengers seat has triggered due to the catalytic conveter putting out enough heat to......trigger the switch under the seat and in turn cause the warning light to come on. CHASSIS ELECTRICAL section has methods of checking out that light/switch.

02 sensor has zip to do with this in any way, shape or form.

I'd say that if your monitoring the fuel pump voltage with a meter, and you turn the key to ON, and it has voltage for a moment or so, then I guess series five cars do have a PRIME feature that I'd not known about.

The relay you hear in the engine bay is the Main Relay that energizes when the key is put to ON. The relay under the dash would problably be the Circuit Opening Relay that controls the fuel pump.

After the car starts, the AFM/ECU keep the fuel pump running by putting a GND on the Circuit Opening Relays second coil. The first coil in the Circuit Opening Relay has a permanent ground and when you HOLD the key to START, that act puts power on the other side of the first coil. Relay now pulls in and stays latched.....as long as the key is held to start.

There's a picture of this in the Fuel and Emissions seciton of the FSM.

The fuel pump resistor relay in front of the air filter assy is part of the power path to the fuel pump. It has to be connected up to the harness.

HAILERS

You might investigate pin 3K on the ECU shown in the jpg in my post above.

It should have the values shown in the attached jpg. NO voltage on it with key OFF. Key to ON should show 12vdc and that 12vdc is coming thru the coil of the circuit opening relay NOT from pin 3K of the ECU.

Then start the engine and 3K should show less than 2vdc because pin 3K is putting a ground on the wire b/t 3K and the Circuit Opening Relay. IF the engine won't run, then push the cone in the afm aft and take a look at 3K's value.

I guess the ECU knows the engine is runing thru a signal from the AFM. ON a series four that is the case. On the series five it's an assumption. I don't own a series five so I can't push the cone in the series five aft to see if the pump runs or not.

You can see from the jpg in my other post, that if you jumper the yellow two pin fuel pump check connector, that does the same as the ECU outputting a gnd on pin 3K. Done

cumberlandrx7

Ok well I feel like an idiot now...

Today I spent all morning trying to trace down any mistake I could have made with the electrical. I am not a complete beginner when it comes to cars but I am also no professional mechanic. I started to second guess the fuel return line and feed line whether or not they were on correctly because I had a friend helping me when we tested the pump and he reconnected them.

I decided to switch them because in my head I recall them being reversed but wasn't sure. After switching them I started the car up and BAM!! no, not an explosion... the car ran for about 10-15 seconds then died lol. Now this isn't really any progress and I wanted to avoid doing this but now is not the time to be lazy. What I am going to do is remove the UIM and make sure the lines are feeding properly for the fuel. Perhaps i'll try and take a video also and hopefully someone will recognize the problem.

The light I have attached to the fuel pump makes me think that the pump is still not running properly because it "primes" it (i think, like I said it turns on for 1 sec when i put it to the "ON" position but it doesn't always do this if I turn the key back and try again it only does it every now and then) also when the car runs for 10-15 seconds the light is on for about 5 seconds then goes out and the car dies about 5 seconds later (maybe less).

If it still sounds like a poor ground connection then i'll try and check every single ground but if it sounds like something else to anyone all ideas are welcome.

cumberlandrx7

Ok well after switching the fuel lines and removing the UIM I found that they were indeed the correct way now. So, I decided to try and start the car again but since the pump was still losing power which lead to the car dying I thought i'd try shorting the yellow test connecter.

With the yellow test connector shorted and the lines fixed the car idles just fine, actually it sounds excellent.

Now my only problem is, where do I go from here lol... how do I fix it so I don't always have to have the test connector shorted???

Also something I noticed is that the tachometer is at 100 rpm when it sounds like a perfect 800 range idle and when I slowly rev it up to 2000-3000 rpm it sounds far higher than that, also the warning lights for exhaust overheat are still on and this is making me start to think that the ECU is causing me extra problems on top of what is already wrong. Is there a way to tune it so that I can use the N3A7 ecu or should I just go with the proper N370???

Ii'm assuming in all this that the p.o. knew alot more than I do and was most deffinately boosting at a high range and seems to have had the engine tuned very well so if possible i'd like to try and make things work with this ecu and keep the nice tuning the p.o. spent so much time acheiving.