Frequent flooding problem
 

Hi,

CAR: 1987 Mazda RX7 TII

So when I bought the car, the previous owner did a flow test for the injectors and all of them were fine. He also said that he replaced the apex seals on a JDM engine and rebuilt the transmission before it sat for about 10 months. When I bought the car, it started right up, but it did have a problem with the oil lines, at which the lines failed and I had to fix them.

I'm pretty sure the flooding problem was existent ever since I've owned the car, where generally during short parking periods the engine will flood. Meaning if I stop at the store or something and come back, the car will have problems starting. But if I leave the car overnight it will start right up.

The previous owner had paperwork documenting that the injectors were flow tested, if that helps any with the injectors being the problem?

I've also read that it could possibly be the rotary engine itself, which I am thinking it may have sustained minor damage from the oil lines completely failing.

The thing is, though, the car drives just fine, however the oil pressure reads low, between 10psi < at idle and at around 35 psi while driving. I'm guessing the low reading is because of an oil sending unit. When the engine is just started up the car will sometimes bog and when the pedal is to the floor the car just sits there not wanting to go faster, but if the pedal isn't decreased as far then it starts to pick up speed.

I'm going to do a compression test when I get the time, but I was wondering is there anything I should be concerned about? I've driven this car around for maybe 10k miles, but it sat for about 7 months because I didn't have time to get to a bad fuel pulsation damper (plus the winter in utah sucks massive male genitalia..)

To sum up,

It doesn't have problems other than bogging during initial start up, and flooding during shorter trips and perhaps a bad oil sender. But I want to know why it wants to keep on flooding on me. (though I could always just install a fuel kill switch, i want to fix the root of the problem)

Do a compression test with the engine warm.

also check that coolant temp sensor. i'm drawing a blank on the parts actual name, but it has a green plug similar to the BAC, and it's located under the alternator. maybe someone else will chime in and offer more info about it

check PRC solenoid and also the water and air temp thermo sensors

together they form the hot start assist system
when all the flags are OK,, the PRC solenoid should show the FPR an atmo vac signal thus raising fuel pressure above normal to cope with fuel percolation after hot starts

if the system is faulty it can add to flooding when cold,, and add to start and stall type bugs when hot

else most people have a pump kill switch to allow the engine to be cranked dry if flooded
and some people add a solenoid between the primary and secondary rails that fails open when the ignition is turned off
this will dump fuel pressure from the feed rail ,, and thus alleviate dripping down injector issues

A fuel cut switch is a "band-aid" but it is also a 5 minute job that will start your car every time it gets flooded. Not a bad thing to have.

quick question guys. it seems that when i initially drive the car after letting it sit for a while, it has no problems starting or running. then when i turn it off and turn it back on within 30 mins, the car will have a little bit of a hard time trying to start and when i accelerate there is a massive loss in power / bogging if i try to accelerate below 3.5k rpms, it will buck very hard sometimes. seems like above 3.5k rpm, it's perfectly fine.

this leads me to believe that something is wrong with the front rotor injectors? (correct term?) I've read that the rotaries in these cars will only engage the rear rotor fuel injectors when the rpm is around 3500 rpm and above.

from sort of piecing this together, i could understand if the front rotor fuel injectors are bad because those ones are for lower rpm acceleration, and could flood the engine no?

could anyone chime in?

You're almost right. Now, I'm no rotary genius, since I only just got one, but this is what I know:

If your car bogs around 3500RPM, it could be one of two problems. There are several grounds, including one under the upper intake manifold, that could be your problem. I'd suggest cleaning and re-installing all of those grounds. Since you'll need to pull the manifold, the second check I would do is of the secondary injectors.

Getting to what you said:

The engine has two separate fuel rails; a primary and a secondary. The primaries are at the bottom of the intake manifold and have two 550cc tan injectors sitting side by side, very close. These operate the engine by themselves up to 3500 rpms or so depending on throttle load. Above that, the two upper injectors nearer to the top of the lower manifold open, and inject supplemental fuel.

I had a very similar problem to yours, but my issue lay in the injectors; my front primary and both secondaries were stuck closed and were passing no fuel whatsoever through them.

The P.O. gave you the paperwork for a set of injectors being flow tested, however, unless I saw those injectors go, and knew for myself that they were indeed sent away, I'd send them again, just for my own satisfaction. It's entirely up to you, though.

There are several write-ups on regrounding the engine; aaroncake's website (the URL of which escapes me at the moment) had a very good writeup on the procedure.

Given that you say the OMP failed, you may wish to do a compression test on the engine. When warm, IIRC, the compression should come up to 100 or so PSI after a few revolutions, and if you hold the bleeder valve on your tester, all three pressure pulses should be even when cranking.

Good luck with it!

Here ya go:
http://www.aaroncake.net/RX-7/grounding.htm

I've regrounded the wires with a 8 gauge wire pretty much everywhere i saw on aaroncakes website, minus maybe one ground. as for similarity in problems, could you describe what your car would do? if they were stuck closed, it means it wouldn't start at all, not flood.

sorry meant the primary fuel injector is one for each rotor, and then the secondaries are kicking in fine, just not the primaries.

guys,

quick question. So I took the upper intake manifold off again to reground the ecu, and also wanted to check the condition of the fuel injectors. I saw that the "INSULATOR" (on page 4b-74 on the FSM) was cracked and dried out. I think that this might be causing my hesitation problem along with my flooding problem? Can anyone chime in on this? It's the rubber/plastic piece that connects the injector into the block.

This works like a charm!!

Yeah the grommets at the bottom of each injector should be soft and pliable not dead hard as a rock causing air leaks at the bottom of the injector. Buy some new ones along with the upper grommets on each injector and throw in four new injector o'rings and a jar of vaseline to lube them prior to install.

IF the problem persists make a fuel cut switch til you can find out what the deal is with the flooding. Low compression causes many of the flood issues.

since you're there, i would check the voltage at the injector clips and visually inspect the terminals inside the wiring harness. it sounds to me like one of the primary injector EGI circuit wires is giving you low voltage issues or the shop that serviced the injectors sent out a faulty one regardless with low output. you can swap the primary and secondary injectors which i would do anyways to see if the issue transitions from low end to top end power loss pointing to the injector being faulty.

if everything tests ok, do a compression test as was mentioned it is the main culprit for hot starting issues.

where can i get a set of insulators locally? does anyone know? (without having to ordering them first from dealer). does local auto parts store carry em?