Hey guys i did some searching and cant find anything this specific, i apologize if this already exists. But my starter cranks way too slow only when the fuel pump is plugged in, when i unplug it then it cranks at about normal speed, i bought a new starter, i cant make a cheap high torque one because i have an na flywheel, and id rather figure this out than go buy the high torque starter from banzai racing, anyone got any ideas on the culprit?

 

This could be a lot of things. A fresh battery is key here as is grounding. For me everything else is down stream of those things. The firewall ground and the one to the starter are probably the most important for this.

Next thing after that is to check the fuel pump wiring or a weak starter? Although a weak starter isn't something I have ever heard of. Usually for me they work or they don't. Maybe I am just inexperienced?

https://www.aaroncake.net/rx-7/grounding.htm

Perhaps someone else has a better take.

 

I have a brand new battery with 750 cold cranking amps fully charged, i have new battery conneters, a brand new starter, (which i bought because the old one was doing the same thing). I also made a chassy ground, including the ground on the bell housing that already exists, i cleaned all the ground and power bonding surfaces and used bonding grease, only thing I can think of is relocating the ground wires that are located on the rotor housing from factory from my understanding, unless they are actually firewall grounds like you said. Or there could possibly be an issue with the pump wiring like you said.

 

What gauge wire did you use for the chassis ground and did you clean the connections to bare metal?

Sorry, the ground on the front shock tower, not the firewall is important. My firewall ground was not connected for years and started fine.

 

I used some ground wire from O'Reilly's thats the same thickness as the stock ground wire, i believe 4 gauge, and i cleaned to bare metal.

 

Ok, let's review.

Large gauge wire from the starter to the battery +, a ground wire from the chassis to the battery - and one from the battery - to the starter bolt... correct? Or the stock wire that is the chassis ground and stater engine ground in one?

 

how slow is "slow"? the engine naturally slows down some when fuel is in the combustion chambers. i couldn't really explain to you why that is other than it is a vapor that displaces compressible air, albeit a very small amount unless you have a stuck open injector issue, then it would slow down a considerable bit more.