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Hey guys, about a day ago I came across the dreaded "Hot start" Issues and I'm going to get it compression checked. I looked online and for some reason Amazon or Atkins rotary dosen't even show a rotary compression tester.
I also tried searching on the forum but a ton of topics I clicked on digressed and never really got a solid answer, So if there is another post up that has already solved my question, I will gladly take this down
BUT here's a weird catch : when I took it to the Mazda dealership for a diagnosis, They had actually shut off the car when it wasn't warmed up all the way when they were done I got lucky and it started right away, must have caught it right when they shut it off.. They also had torn some parts of the engine to check a couple of things i.e the Oil lines, and the OMP, I noticed because some of my work was gone.
But ever since then I've been having some issues starting. I do not have a Catalytic converter as it is gutted, I do have the LS coil swap kit, but it is starting to look awfully old.. I already have new NGK plugs and I also have a stronger starter sitting around so I might as well install those in the meantime. MAF was just cleaned but it's still throwing a code so I'm going to double-check everything again, make sure it's all in the right place. I will update this thread if what I do actually solves the problem.
The car still has a ton of power, and it still does have the oil leak in my previous posts because I am waiting on new gaskets and O-rings to arrive. I was planning on getting rid of the leak regardless of the condition the motor was in. The dealership I went to, to repair the leak was only going to charge me 250 or less to reinstall lines and new gaskets and new o-rings, so I figured why not? They did also have 2-3 RX8's sitting in their shop being worked on as well. One of them actually had a recall being installed.
I don't plan on selling my car in the near future, even after having a rebuild as I have fallen in love with the dreaded rotary. What testers would you guys recommend? Or is there a way to convert using a Piston tester and some formulas? Thanks in advance!
I also should note that the car takes 15-10 seconds to start when hot, Regardless after immediately shutting down or after a 30 min wait. I also might think its a bad fuel pump, but it starts completely fine when cold..
Last edited by RX-8 40th Anniversary; 12-04-2020 at 05:15 PM.
Get ahold of Steve at https://www.rotarycompressiontester.com/ He builds them and sells them to the community at a very reasonable price. Its an amazing tool and one of my favorites in my tool box!
Get ahold of Steve at https://www.rotarycompressiontester.com/ He builds them and sells them to the community at a very reasonable price. Its an amazing tool and one of my favorites in my tool box!
Yup, can confirm its made me more money than cost me.
Also I assume you reset the NVRAM?
(20 brake pedal stomp)
While you're waiting to check your compression, and if you plan on keeping it no matter what, you could replace your coils and wires to eliminate that possibility, or check them with an HEI tester, which can save you money and is a good little cheap tool for a rotary tool box.
Do you have the OEM mounting bracket?
Idk what the GM coils cost but you can get lifetime OEM coils for around $35.
Also I assume you reset the NVRAM?
(20 brake pedal stomp)
While you're waiting to check your compression, and if you plan on keeping it no matter what, you could replace your coils and wires to eliminate that possibility, or check them with an HEI tester, which can save you money and is a good little cheap tool for a rotary tool box.
Do you have the OEM mounting bracket?
Idk what the GM coils cost but you can get lifetime OEM coils for around $35.
I have not tried that yet, but I am also very much so more confident that the plugs are the issue, one is cracked, and theyre all jammed to hell and Ive been using wd40 to try and untighten them. I believe I have the OEM bracket... but im not so sure. I'll double check. Also any tips on removing cracked and tightened up plugs? 🤣
I have not tried that yet, but I am also very much so more confident that the plugs are the issue, one is cracked, and theyre all jammed to hell and Ive been using wd40 to try and untighten them. I believe I have the OEM bracket... but im not so sure. I'll double check. Also any tips on removing cracked and tightened up plugs? 🤣
Take your wheel off, and warm up your engine for a few minutes, but just enough to get it hot. Tag your wires and pull them off the plugs, spray it with PB Blaster and let it sit for a couple of hours, or overnight.
If you don't have any, get some.
Spray it several times while warm.
If you have a 1/2" drive ratchet or even better, an impact gun, try it with the shortest extension possible.
You might be able to 'rent' an electric impact for free if you don't have an air compressor.
If you find one, ask if they have a deep 13/16" torque stick to go with it.
I'm not sure they'll reach on a spark plug but it's worth asking about.
The shorter length you have, the better. You lose torque with longer extensions.
Also if you don't have a torque wrench, buy or rent one so you never overtighten your plugs, or anything else for that matter.
Breaking off or stripping bolts sucks.
I managed to get them off with an impact driver, but I will certainly keep this advice for the future! Thank you for helping me out by the way, I do appreciate it.
I always very lightly lube the threads of the spark plugs with some Marvel Mystery Oil before reinstalling. I've done this for many years and have never had a plug seize on me.
BUT here's a weird catch : when I took it to the Mazda dealership for a diagnosis, They had actually shut off the car when it wasn't warmed up all the way when they were done I got lucky and it started right away, must have caught it right when they shut it off.. They also had torn some parts of the engine to check a couple of things i.e the Oil lines, and the OMP, I noticed because some of my work was gone.
But ever since then I've been having some issues starting. I do not have a Catalytic converter as it is gutted, I do have the LS coil swap kit, but it is starting to look awfully old.. I already have new NGK plugs and I also have a stronger starter sitting around so I might as well install those in the meantime. MAF was just cleaned but it's still throwing a code so I'm going to double-check everything again, make sure it's all in the right place. I will update this thread if what I do actually solves the problem.
The car still has a ton of power, and it still does have the oil leak in my previous posts because I am waiting on new gaskets and O-rings to arrive. I was planning on getting rid of the leak regardless of the condition the motor was in. The dealership I went to, to repair the leak was only going to charge me 250 or less to reinstall lines and new gaskets and new o-rings, so I figured why not? They did also have 2-3 RX8's sitting in their shop being worked on as well. One of them actually had a recall being installed.
I also should note that the car takes 15-10 seconds to start when hot, Regardless after immediately shutting down or after a 30 min wait. I also might think its a bad fuel pump, but it starts completely fine when cold..
Shutting the car off before letting it fully warmed up(cold start,cold shutdown) really could only cause flooding, this was more prevalent on older 13b engines. Flooding would point towards a type of fluid lingering in your combustion chamber. Typically with the Renesis engines around 100k miles the coolant jackets give up and you'll see plumes of white smoke until the engine reaches temperature. Once the engine gets up to temp the seal expands enough to reseal the coolant system. So, I suppose shutting down cold could create enough pressure in the coolant system to flood the engine due to the seal not resealing. I suppose if the spark plugs get fouled enough you could just flood the engine with unburnt gas. Then the question would be what fouled the plugs. In short, the dealer shutting the car off cold wouldn't cause any effect that lasted more than one start up.
Are you saying that after the car came back from the Mazda dealer it suddenly is having the hotstart issue and you had no symptoms before?
In terms of power, a low compression motor will have less power than a newer motor obviously, but it definitely isn't something you will feel. Actually this is why there are many threads of people having hot start issues but think the engine is still good because it seems to still run like normal once it does get started.
The general way to see if a fuel pump is bad is to warm the car up to normal running temp and then see if it will go above ~6krpm. If it revs fully to redline without going limp it is most likely fine. I doubt the pump is heat soaking the fuel enough at idle that it reaches a point where it won't for some reason be able to start the car at the same temperature but somehow go to 9krpm.
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My advice from someone who brought a Ren engine to such low compression it had trouble starting cold, it is definitely the right choice to buy a rotary compression tester. I personally have no faith in random mazda dealers doing anything right. I've seen dealers give compression tests that say the engine is at 130psi compression and then the personal tester gives a 70-80psi reading>>hot start issue.
Shutting the car off before letting it fully warmed up(cold start,cold shutdown) really could only cause flooding, this was more prevalent on older 13b engines. Flooding would point towards a type of fluid lingering in your combustion chamber. Typically with the Renesis engines around 100k miles the coolant jackets give up and you'll see plumes of white smoke until the engine reaches temperature. Once the engine gets up to temp the seal expands enough to reseal the coolant system. So, I suppose shutting down cold could create enough pressure in the coolant system to flood the engine due to the seal not resealing. I suppose if the spark plugs get fouled enough you could just flood the engine with unburnt gas. Then the question would be what fouled the plugs. In short, the dealer shutting the car off cold wouldn't cause any effect that lasted more than one start up.
Are you saying that after the car came back from the Mazda dealer it suddenly is having the hotstart issue and you had no symptoms before?
In terms of power, a low compression motor will have less power than a newer motor obviously, but it definitely isn't something you will feel. Actually this is why there are many threads of people having hot start issues but think the engine is still good because it seems to still run like normal once it does get started.
The general way to see if a fuel pump is bad is to warm the car up to normal running temp and then see if it will go above ~6krpm. If it revs fully to redline without going limp it is most likely fine. I doubt the pump is heat soaking the fuel enough at idle that it reaches a point where it won't for some reason be able to start the car at the same temperature but somehow go to 9krpm.
-----------
My advice from someone who brought a Ren engine to such low compression it had trouble starting cold, it is definitely the right choice to buy a rotary compression tester. I personally have no faith in random mazda dealers doing anything right. I've seen dealers give compression tests that say the engine is at 130psi compression and then the personal tester gives a 70-80psi reading>>hot start issue.
Yes actually.. I had no issues starting it up before I took it to them to diagnose the oil leak. I also have a foul suspect its the coils because they are awfully old, but I can't get anywork done as of now because I have to qurantine. The coil wires also don't seem to match up accordingly to the plugs so that's another thing im going to try. I am very suspective of this dealership on the otherhand, but I have no one else to go to really
I built one with an off-brand arduino nano and the cheapest parts I could find on amazon, loosely based on THIS. Probably under $40 CAD into it. Still need to make an enclosure of some sort for it.I should publish the updated code for it too....
I built one with an off-brand arduino nano and the cheapest parts I could find on amazon, loosely based on THIS. Probably under $40 CAD into it. Still need to make an enclosure of some sort for it.I should publish the updated code for it too....
That's awfully impressive... why buy one when you can DIY I'll end up finding some compression tester somewhere, in the mean time I'll install the starter I had sitting and double check the coils..
12-04-2020, 05:11 PM
Recommended Engine testers?
I got lucky and it started right away, must have caught it right when they shut it off.. They also had torn some parts of the engine to check a couple of things i.e the Oil lines, and the OMP, I noticed because some of my work was gone.
I'll end up finding some compression tester somewhere, in the mean time I'll install the starter I had sitting and double check the coils.. 
