Got a 10th ae with an engine rebuilt by Juan Delgado (Mazda employee/rotary expert). It was supposedly running fine and then started flooding randomly. I installed a fuel pump switch and on a few occasions got it to start and run for a couple minutes. But it's unpredictable when it will and won't start.

Compression test showed even pulses front and rear. 95psi rear/ 65 front. I know the front is low, but not soo much as to make it sporadically start/run great for a minute or so and then not start.

Installed an rtek 2.1 just to check sensor inputs to the ecu. All inputs seem normal.

Tried installing a different tps/afm/boost sensor all at different times to no avail.

Any ideas? It's soo intermittent that I can't seem to figure out what changes when it starts beautifully and runs smoothly.

Chris

 

Also, when it does run it smokes slightly and when it starts running badly (starts missing and shuddering before it wants to shut off) it smokes more so.

 

Everything grounded?

 

Yes, removed/cleaned the engine ground for the ecu and the engine to body ground as well.

 

Are you positive it was flooding and just not getting proper fuel pressure?
Have you checked the fuel pressure/fuel pump?

 

It's flooding, I'm certain of it.

Fuel pump is a walbro (previous owner) and fuel pressure never rises above 42 psi. I tested it fearing the walbro was greatly outflowing the stock fpr, but not the case.

 

Seems you're beating around the bush a little bit. 65psi on any face is not good imo. You want 75+ ideally and personally I like them higher than that. Do you get just one or two+ pulses at 65psi?

That paired with the smoke sounds like a seal could be sticking. I'm no expert by any means but you've got to think about it fundamentally sometimes. If you get good fuel pressure and you get spark, check inputs. If they're good and your coils are straight, don't you think it'd be time to address the lack of compression on fhe front rotor?

Personally I would have torn down to see why there was real low compression.

 

I agree with your diagnosis typically, and agree it may just be an intermittently stuck seal internally. I was looking at other opinions/options on the subject before I tore it down. It still seems odd that the car has ran soo well periodically and now will not even try to fire up. It's as though it floods within the first second of firing with the fuel pump on.

As for the compression, I want to know why the compression isn't higher but I also think the car has almost no miles on the rebuild. I know the guy before me drove it for a couple hundred miles.

 

Typically any minor loss in compression will be restored within 100 miles on the engine. If the PO drove it a few hundred miles before you got it, something could have been not quite right in the build. It happens to everyone, even the pros and I am certainly no exception.

If your voltages, resistances and continuity check out all over, you get the proper pressure in the lines and at the rail, and your filter is fresh, it only makes sense that it's an internal issue.

Does starting it with the pedal to the floor in a 10AE/S4 cut fuel like it does in an S5?

 

I understand, and agree everyone makes mistakes. I just don't understand why it floods soo quickly. It's as though it's a fuel related problem in my eyes, although the compression is not above reproach. The conclusion I believe I have come to is just to get to the injectors and spin a CAS by hand to check spray pattern and proper opening and closing. If that checks out I will keep disassembling it for inspection/rebuild.

Also, no the 10th ae will not fuel cut at full throttle like an s5.

 

That would be a surefire way to get some solid results. If everything checks out there, pull it and tear it down. Post results.

 

Any updates on this, guy?

 

I wish, going to dgrr in my dd vert instead so I've been working on it. I would imagine it will be after dgrr before I get to do this.

 

It's alright man at least you can make it there.