bg894

iTrader: (1)

Hi guys,

New member, but I've lurked for a bit trying to get my RX7 running. Long story short, let me break down whats happening and what I have tried...

Problem: Motor cranks but doesn't start up

• I have verified that all the plugs and wires are good, they all produce a spark.
  
• I installed a new fuel pump (to fix what the prior owner said was wrong)
  
• I have used multiple different car batteries, to eliminate any possibilities there.
  
• I have pulled the EGI comp fuse and followed unflooding procedures.

I have fuel... I have spark and I'm stumped. I'm starting to think bad compression, but I have no present way of testing that.

satch

iTrader: (1)

Have you ever been able to start the car or not? You could try starter fluid (1 to 2 seconds at most). You could try pull starting the car. And weak spark is an animal of its own regardless of compression so you might want to focus on that. Could be the coils/igniters themselves or it could be poor grounding which is achieved by the coil unit having good contact/mating w/the fender. If you question the contact surface you could clean it. Also, you could place a small amount of oil in the rotor housings to create added compression. Sometimes a flooded engine is a beast to unflood.

bg894

iTrader: (1)

Hey Satch thanks for the reply!

I have tried starter fluid to no avail. I will go ahead and try checking the contact surfaces on the coils. While following unflooding procedures I put oil through both leading spark plug holes.

My next question is I've heard a lot about the fuel pump relay, which I can't seem to locate between google and the service manual that the vehicles previous owner included. Not sure if this is a potential factor.

satch

iTrader: (1)

It's located under the dash just to the right of the steering wheel column. Starter fluid should have at least got the car to start if there was an absence of fuel so that it would not start would make one think of spark as being the cause.

How did you check the plugs and wires? How do you know you have fuel?

bg894

iTrader: (1)

That's my thought at this point, that there must be some spark related issue.

Basically I pulled wires to make sure they all sparked, which they did. I then connected the respective plugs into each wire and tested one after another. Each plug made a spark. Now whether or not it's enough spark, I'm not sure how to gauge.

Regarding fuel, the pump is running and getting fuel into the motor because of the flooding that has happened. I haven't tested to see if there's a bad fuel filter at play. And regarding injectors, etc that is an area outside of my knowledge. So any info is appreciated as well.

While I had the fusebox open I noticed what looked like a bubbled up plastic cover on my main fuse. If that was blown, would I even be getting this far?

satch

iTrader: (1)

You would not be getting this far if it were, but it would be best to replace it though at some time (it's screwed in place from the side as it doesn't just pull out). You should check compression. Usually, you could rent or borrow a tester from a local auto parts store.

The color of the spark should be bluish in nature and not yellow/orange.

Also, with feeling, have you ever got this car to start before?

bg894

iTrader: (1)

I will check the spark to verify the color.

I have never had this car running. Purchased it for next to nothing the other day from someone saying it needed a fuel pump and would be back on its feet. It has sat since last fall in Vermont cold weather conditions. The prior owner bought the new plugs and wires, but had them installed incorrectly. I have remedied that much, as well as installed a new fuel pump but here I am still scratching my head.

satch

iTrader: (1)

The lead coil is what will get the car started so you could focus on that (spark). Check the Brown/White wire of the boost sensor to confirm it has 5 volts w/key to on. And a large vacuum leak could prevent a car from starting. Also, incorrect timing would cause a no start issue as well. You could always check the fuel pressure w/a gauge. And do you have any components in the engine bay disconnected and so on such as the intake cowl from the AFM or throttle body?

satch

iTrader: (1)

And you would need an NA fuel pump replacement and not from a turbo for that would be overkill and likely flood the engine.

bg894

iTrader: (1)

I have the stock airbox in. I purchased a 255lph fuel pump that was compatible, but you do bring up a good point with providing too much fuel. I suppose a fuel pressure gauge could clear that up.

Regarding timing I've seen a lot of talk regarding the CAS but given the cars history I can't see a reason it would be out of time. Perhaps something worth looking into as well

satch

iTrader: (1)

I believe that's a high flow fuel pump and is too much for an NA.

bg894

iTrader: (1)

It was indeed advertised as a 255lph high flow fuel pump.

Maybe I should look into a lower flow pump? I'm curious if the injectors would fight off the extra pressure or not.


I should give it a fuel pressure test, but also a dreaded compression test...

ps: FSM states that the stock fuel pump has a 1.3 liter per min average output, which translates to around 80 lph.... have we found my problem?

satch

iTrader: (1)

The FPR is supposed to regulate the pressure but the pump you have will overwhelm the regulator. Additionally, taking a compression test will cause the results to be lower than normal w/a flooded engine. You really need to expel the fuel from the housings and make sure the plugs are not wet/fouled.

You need the pump for an NA as you have a turbo sized pump currently.

bg894

iTrader: (1)

My next steps will be

• Crank the engine over with the egi fuses out to blow out remaining gasoline
• Ensure spark plugs are dry and oil is put into rotor housing
• Purchase and install this fuel pump (Mazda RX7 OEM Replacement Fuel Pump 1986-1995 - TREperformance.com)

It looks to me like that pump would be optimal given the very similar LPH output to stock (100LPH as opposed to roughly 80LPH on the OEM)

If you have any other suggestions before I move forward, I'm completely open to them. I really appreciate your help thus far.

satch

iTrader: (1)

Looks like a good plan of attack.

bg894

iTrader: (1)

I have installed a functioning OEM fuel pump for the NA. Blew excess gas out of the motor, cleaned up the plugs but no luck.

I'm wondering if I should spring for a new set of lead plugs at least. Also as another update, I realized the prior owner installed plugs and wires incorrectly initially. He had the wires mixed up and the plugs were opposite (L, T not T, L). Could this have cause any damage? I have since fixed the placement of both.

UPDATE: After further investigation my plugs are sparking orange rather than blue. Thoughts?

bg894

iTrader: (1)

This all appears to me like it is spark related at this point. Any sure fired ways to tell whats up? Both coils spark the plugs with a relatively weak looking, orange spark.

satch

iTrader: (1)

Did you try cleaning up the coil ground (mating surface between the coil and fender). I would think mixed up plugs would just lead to a poorly running machine. Just to make sure, leading are on top of the rotor housings.

bg894

iTrader: (1)

Cleaned up the grounding surfaces to no avail.

satch

iTrader: (1)

Did you check the plug wires according to spec as stated in the FSM (a resistance check)? If they read properly then perhaps the problem can be narrowed down to the plugs or coils.

And a compression check is a likely course of action at this point especially since you've never been able to start the car..

bg894

iTrader: (1)

I did not perform a resistance check... I need to read up on that.

Also, I was unable to rent a compression tester for free, so I have one coming thanks to Amazon. If my compression looks good... whats next?

satch

iTrader: (1)

You need to verify that the injectors are high ohm or low ohm. Low ohm requires the resistor box or in line resistors while the high ohm variety requires neither.

bg894

iTrader: (1)

Will do. Gives me more incentive to get a decent volt meter... Either way I have the top injectors out so perfect timing.

satch

iTrader: (1)

They're the ones used for starting so that's good.