Hello I'm new here and I have a major problem with my car. I hope you don't mind a long drawn out explanation but here it goes. So I have an 87 na I basically swapped over with a 93 13brew streetport engine and I also have a place here in Boise ID working on the wiring for it. So we got the wiring from the 93 and are running a reflash ecu with tuning for aftermarket exhaust and refined ignition timing etc. The upgrades I have are :a 3 inch downpipe with magnaflow cat and muffler. I also have a prolite flywheel with 6 puck clutch. The engine is mild streetport with about 5000 miles. I have new rebuilt twin turbos on it. I also have a fmic with two hks blow off valves. All new silicone emissions hoses. New coil packs and plugs and wires. Cold air intake. The engine also had turbo II low compression rotors put in it. Now, to the problem, I have a major issue with cold starting. I have to turn the engine over about 20 times to get it to finally start. While turning it over it fumbles and then follows with a loud backfire about every 6th or 7th time I turn the ignition over. I also don't know if its normal but I can here the fuel pump constantly prime when I turn the key over which I'm told is normal but I thought it was a little unusual. When it finally starts it seems like it is running great. The shop that has the car says it is running to rich though. When its warmed up the car starts with no hesitation. I hope I didn't bore anyone with my long drawn out issue but I really would appreciate any ideas. Pettit Racing said it could be a bad crank sensor or air temp or coolant sensor. They said it shouldn't have any problems with start up based up my upgrades but maybe they don't know for sure. Again I appreciate any feedback. Thanks again.

 

I'm not familiar with the intricacies of the FD EFI system, so maybe someone will chime in.

My first guess is that an engine with 5K on it, depending on how long it has been sitting and what injectors are installed, may simply be still quite low on compression and may need some more run time.

If it is also running excessively rich, then it may be very hard to start due to always being on the edge of flooding.

Yes, it is normal for the fuel pump to run during cranking.

If it starts warm with no problem, test the ECT sensor. Perhaps it is not reading correctly and the ECU is defaulting to 80 degrees.

I'm curious though, why go through all the trouble to adapt a stock EFI system when it would have been a lot less work to use a full standalone, and move versatile in the end? Especially when it would make troubleshooting problems like this easy.

 

You know its funny you say that because i swear it was only running like 70 psi on one rotor and 75 psi on the other. My local maztech insists the engine is fine though. The ect plugs into the water pump neck right? The hardest part was the wiring which I payed someone to do and eventually I wanted to get a pfc to work with the twins. So now if I do get a pfc it will hook right up. But i can see why you ask.

 

The ECT is on that big water pump housing, and the back I believe on the FD.

A brand new engine with larger injectors will flood easily, which will lower compression.

70/75 PSI is pretty low.

 

sounds like a combination of a **** engine with **** spark plugs.

and you should have kept the 9.0:1 rotors, who talked you into using the low compression rotors on a twin turbo setup?

 

Yea I thought compression was low. Its weird that both rotors are though and I wonder if this could also be partly because they are turbo II rotors. The spark plugs are new ngks with platinum plugs and new coil pacs. The ignitor is old but I think its still functioning. If I have to rebuild the engine, I will make sure to get 93 rotors for it. Its just how I bought the engine unfortunately. I know it is definitely suited better for a single turbo pushing crazy amounts of boost. When an engine is bad, doesn't it more likely have problems on start up after its warm? I guess a bad coolant seal could do this

 

 

sounds like a bridge, idling at 3k, also slow to rev. ie lack of response which is typical of low compression engines or it just has a junk tune on it, but you said it only has 75psi which is low to the point of hard starting issues.

once a rotary engine is running, if compression is even across the board it will sound perfectly normal. but that doesn't mean it is healthy.

FD control systems are very comparative of most other MAP based standalone ECUs, they will still have difficulty starting a rotary if you begin dipping below 80psi of cranking compression. ie flooding issues, backfiring and popping while cranking until it either starts or fouls the spark plugs.

 

so your leaning on more of it being bad apex seals? any way I could test that? I really need to do a champagne test. could it be possible that I have blown coolant seals. Maybe it is just leaking into one side of the engine and effects the one rotor on cold start. When it clears out the water from turning over, it actually starts?

 

can an aftermarket ecu help an engine run way better on such low compression. or am i going to have starting issues with something so low. I have these specialists working on it at maztech and they are insistant upon this engine being good.

 

a standalone will allow you to adjust cranking fuel to make a low compression engine easier to start, yes. but it still isn't ideal and won't always correct for flooding issues of a non-healthy engine.

coolant leaking into a chamber overnight can also cause difficulty starting but it will sound like pure *** for about 30 second while cleaning out the affected chamber. sound is as if only half the engine is running, then all of a sudden it clears up and runs smooth. hint of sweet smell from exhaust is also an indicator.

if they are insistent on the engine being fine while handing you a sheet with those cranking compression figures you may want to think twice about having them do further work on it.

 

So it fires right up when @ full op-temp?
Sounds like not proper fuel delivery (lean) when cold.

How was compression done?
Standard comp gauge?
What's the RPM while cranking over?

If the rotor housings are in good shape (and seals are good), wouldn't @ 5K miles comp be w/in spec at least ?

Might just be a serious vacuum leak.

 

Are you sure the map sensor is being supplied with a good pressure signal? My FD will smoke like a freight train and stumble all over the place if the little hose to the map gets knocked off.

 

so is it normal for a bad engine to have equally bad compression on both rotors? I used a standard tester from harbor freight. i have had my doubts about this place but they are the only shop in boise. Ill prolly give them two more months before I demand my car back. After warm up it starts up first try. I replaced all hoses with silicone so i really dont think there is a vacuum leak. I got a used map sensor online, i wonder if that could cause such problems?