Howdy! I posted a build thread but thought I’d come here directly for help on this issue. Quick background: It’s an ‘84 SE that sat for 10-11 years. I dropped the fuel tank, cleaned the hell out of it, and sealed it with POR15. I removed the fuel lines from the tank to the fuel pump and filter. I cleaned the fuel pump the best I could and actually got it pumping again. Initially it wouldn’t even hum. I don’t know what the flow rate and or pressure is supposed to be on it and I don’t know how to measure those parameters anyway. The fuel filter is new. I got it back together and disconnected the fuel line near the engine. I then powered the fuel pump directly until nothing but clean fuel was spilling out of the fuel line in the engine bay. I reconnected that line and plugged the fuel pump back into the two wire connected behind the driver seat. The car cranks but won’t fire. If I pour a small bit of raw fuel into the air filter box the engine will start and run for a second or two then dies. I went back and checked to see if the fuel is being pumped during cranking with the OEM wiring and it does move fuel while cranking.

So, I’m wondering if the injectors are clogged from sitting for so long. I honestly don’t know where the injectors are and if I can remove them to clean them or replace them. Any help
or suggestions would be really appreciated. I’ve attached photos of the engine so you can see what’s there. The radiator is missing because I have yet to install the new replacement one. Could that have anything to do with it? I guess it’s possible that it won’t send fuel to the engine if the no coolant warning is on or something like that?

 

Reads like the EFI system isn't firing the Fuel Injectors, likely because your Trailing Ignitor is bad, your Trailing Coil is bad, or the wiring in between is bad. The SE only fires the Injectors when the engine is spinning as defined by the AFM door being open - which closes the Fuel Pump circuit supplying fuel - AND has ignition as defined by the Trailing Coil sparking.

There are no other lock-outs in the system which would prevent it from starting; it's not that smart. However, once you do get it running, if there's no coolant to have a temperature reading, it will never get out of cold-start mode and will be running rich, and at a higher than normal RPM.

You really shouldn't be running the engine without a closed up cooling system and a working radiator, anyway. You're begging for an overheat in a rotary engine by doing so,

 

Thanks @LongDuck ! Yeah, working on getting the replacement radiator in now. I certainly wouldn’t run it without one. The two times it ran by putting a small amount of fuel in the air box it was for no longer than two seconds or so. Incidentally, the new radiator doesn’t have a spot for a sensor that was on the bottom of the original unit. I’ll add a pic where I have the sensor location circled. I’d be really grateful if anyone could tell me what that sensor does and if I need to somehow hook it up to the new radiator. In the meantime I have a lot of reading up on the terms that you gave me about the fuel injection. It’s all new to me so I’m gonna have to get my schooling on about it.

 

I pretty sure that sensor is just for the sub-zero starting assist system. Not needed unless its very very cold (0F or less).

 

Yeah, I don’t ever plan on driving it in the winter. So, can I just leave it disconnected?

 

Short answer; yes.

Long answer; most of the Sub-Zero Assist systems out there no longer work anyway, as most were dead within years of being sold. This system used the freeze temp sensor as mentioned to determine if the car needed antifreeze (90/10 AF:water) injected into the center housing intake path through a squirt nozzle attached to a separate tank with it's own 12v pump. Much like a windshield washer tank, many of these were removed, and even Mazda had a silent recall to disable the system rather than have customers asking for them to be repaired. In reality, they likely didn't work all that well in sub-zero temps, anyway - as the fluid was designed to lubricate the chamber and rotor seals and improve compression.

On the SE, the squirter mechanism is located on the top surface of the lower intake manifold and has a rudimentary one-way valve made up of a bimetal strip that only opens at sub-zero temps, allowing the Start Assist fluid to get by. All other times, it's closed to prevent a vacuum leak, but I put a hose cap over the fluid inlet anyway.

 

Back to the issue of the Fuel Pump and how to test it; I'm of the belief that our SE Fuel Pumps don't typically fail very often - if they get used regularly (*run at least monthly). The problem is that when they sit, any moisture in the Fuel will corrode the internal parts and seize the pump. Many can be resurrected with solvents and then back to 100% function, which is pretty amazing. I changed my Fuel Pump at 225k miles (*you read that right) and only because I was tracing down a short that caused a no-start, and I'd exhausted all other options. The Fuel Pump wasn't the problem, and it still sits on my parts shelf as a backup.

Point being, if the pump is running, it's probably putting out proper volume and pressure to run the measly 2×680cc Fuel Injectors of the stock system. The pressure only has to meet 33psi at idle and bump to 44psi at WOT for the Fuel Rail to get enough fuel so the Injectors can be managed with pulse duration, as determined by the ECU. The engine spends 95+% of its time in open map mode, as closed map ONLY occurs when in 5th gear cruising at steady speeds, and uses the O2 sensor for map tailoring. Expect that way the car should be driven aligns with 1980s Bosche L-Jetronic design and is simply a map for RPM and load, i.e. vacuum.

There are ways to install an inline Fuel Pressure Gauge for EFI systems, but that's overly complicated given the above. Certainly do the FSM volume test at the firewall, but I suspect you'll find the pump is working fine.

Feel free to start a new thread if his is a new issue. Good luck,

EDIT: I went back and read your original post; if you got a lot of gunk in the tank and fuel pump, your Injectors probably did, too. You're going to need to pull the Upper Intake Manifold and remove the Fuel Rail to expose the Injectors, and then you'll know what you're dealing with. Get that apart, post some pics of what you find, and let's go from there.

 

I got the injectors out today. They look pretty dirty. I’m planning on sending them
off to be cleaned and flow tested. I found rcfuelinjection.com I wonder if they’re a good resource or if there’s someone better out there?

The fuel rail looked clean and had fuel in it so we know it’s getting fuel up to that point. I need to read up on how the injectors actually work. I know they’re controlled by the ECU. I hope it’s not a problem with the ECU because I don’t know much about them or how to troubleshoot them.​​​​​​​

 

I've used RC Engineering a few times now for Injector service, and they do an excellent job. Those look a little dirty, but they're not obviously leaky due to broken body or spray housings. A new set of top & bottom grommets should be installed when they come back to ensure you have a good seal (*aka Injector Seal Kit) and no vacuum leaks.

As I mentioned in the other thread, be careful with the Injector connectors as the spring wire clip can sometimes crack the connectors, and then you'll need to splice new connectors into the wiring harness. Apart from that risk - good job getting it apart, and be sure to install new intake manifold gaskets on reassembly.

 

Thanks @LongDuck ! Yeah, the clips were a pain in the ****. One little corner broke each clip. I think they should still hold fine though. I’m not opposed to splicing in new ones though. The plastic on them is way brittle.

I ordered a new intake manifold gasket. I also want to replace the short pieces of fuel hose that connect to the fuel rail. Hopefully one of the local auto parts stores has the correct stuff.

 

For Fuel Feed and Return, use ONLY FUEL INJECTION RATED hose. I've seen normal low pressure fuel hosed used before that degraded from getting pumped up with pressure, and when it starts to fail, it creates a fine mist of fuel spray - obviously a fire risk in an engine bay.

Fuel Injection hose will have that printed directly on the side. Be sure of what you're buying. It's important.

 

Got the injectors back from RC today. They look great. I’ll post a pic of the testing before and after cleaning. It does have me already thinking: According to RC’s test it’s was putting out fuel, albeit dripping, before cleaning. That makes me wonder if the car should have ran somewhat with the injectors as they were? I hope it’s not an electrical issue, say with the ECU for example. Anyway, I hope to be able to install the injectors in the next few days. Some of the videos I’ve watched show that they soak the injectors in gasoline before installing them. Is that the proper step? Also, do I need to lubricate the new o-rings with anything prior to installation?

 

Regardless if they were 100% the culprit, it's always good practice to have injectors cleaned so you're starting with a fresh base to go from. The car will run better all around having done this, so it's the right move.

Be sure to apply a little bit of oil to the o-rings before you push them into the seats, this will prevent the o-ring from being damaged or not seating all the way.

 

Also. "DRIPPING" is not a spray pattern. Liquid fuel doesn't burn - fuel vapor burns. The only way that fuel vapor exists is that your Fuel Injectors spray a mist of fuel at high pressure directly onto the spray diffusers down inside the Fuel Injector bore on the center housing. These brown carbon fiber diffusers ensure that the spray is completely atomized before it's drawn into the combustion chambers. Liquid fuel will not start a car (*I know somebody's going to argue with me on this, but it's basic chemistry...).

There's no need to soak them in gasoline before installing. Just ensure they're sealed up with new grommets, the Fuel Rail is seated correctly and that they don't leak pressure BEFORE you reinstall the Upper Intake Manifold. The test procedure is well-documented here when you search.

I have a feeling your car is going to fire right up without any other changes, so resist the urge to tinker with stuff. Just put it back together and see how it goes; you may be pleasantly surprised. Good luck,

 

I really appreciate the guidance offered here. You guys are great! I had a little time this afternoon to work on the RX-7. I tested the fuel pressure at the supply line for the fuel rail. It’s looks good. That’s crazy considering the fuel pump didn’t move one bit when I first tried it out. Looks like it’s making 54psi. Next I put the whole injectors in the fuel rail and secured them in place with zip ties. After shorting the fuel pump plug I checked it for leaks. The pulse dampener was leaking a little from where the Phillips head screw was. Tightening that down stopped the leak. I let it sit pressurized for 30 minutes and the injectors didn’t leak. I’m still a little concerned about the fuel dampener leaking but I’ll check it again before I install the upper air intake. I quickly tested the injectors by pulsing them with 12v power and they each sprayed nicely. Getting the old upper air intake gasket material off the lower air intake was a pain! I got that off and called it a night. Tomorrow I’ll install the injectors and fuel rail and check it again for leaks before I replace the air plenum or “dynamic chamber”.

 

Good progress. I'm anxious to know if it started! Good luck!

 

It runs! Started right up. That’s the good news. The bad news is that the fuel rail pulsation dampener is leaking again. It’s leaking out of the small Phillips head screw. I tested it before I finished installing the dynamic chamber and it didn’t leak. Maybe once it got warm from running? Anyway, I ordered a new one. Might as well replace it with a new one and nip that problem in the bud. I really appreciate all the help from @LongDuck and @GtiKyle and the others who have given me helpful tips and encouragement. It feels good getting to this point. I’ll be posting more stuff on my build thread as this was kind of a side note post. Thanks again guys!

 

You're welcome - glad it's back up and running. The Pulsation Dampner on the Fuel Rail matches the one attached to the Fuel Pump so that you don't get harmonic hammer effect at the Fuel Injectors. That yours is leaking is odd, as these typically don't go bad. The 2nd Gen cars had problems with leaky Dampners which is attributed to several engine fires, so it's good that you're replacing it. Let us know how it drives,