Flooding after car is warmed up

87GN87GN

New Member
Hey guys, need some help with an odd flooding issue. Have an 87 GN with 93,000 miles. Over the last 8 months I have done alot of upgrades:

Scanmaster and gauges
Turbonetics TE-44
TR-6 ignition
60 pound injectors
Turbo Tweak chip burned for my setup and injectors
Alky control Alky system
New stock ECM
Plenum plate
Walbro 340 hot-wired
Adjustable FPR

The car runs GREAT, smooth and strong right up to 22 pounds of boost which is where I have it dialed in at. The issue is getting it started. When the car is cold it fires right up and goes right into a nice smooth idle. But after the car is fully warmed up, if you turn it off and try to restart a few seconds later, it just floods itself and is almost impossible to get started. Using the "clear flood" feature with the pedal on the mat does help some but even then sometimes it is not possible to get it going. You can smell gas and if the car does fire up it puts out the classic cloud of black fuel smoke and stumles and sputters along until all the excess fuel is burned up - and then it runs good again. When I have this issue, which is almost every time, If you let the car sit for 15-20 minutes it will fire right up with no problem.

One thing I have noticed recently which I think might be related (not sure if it started exactly when the hard starting issue began but it is close) is that when the key is turned half way I get no data on the Scanmaster. This also only happens when the engine is fully warmed up, when cold I have data with key half way. My SM input wire is soldered onto the ECM wire about a foot from where the main ECM plug is, the connection is good. I also tried attaching a scantool to the ALDL port and no data there either when the car is warmed up and key half way. However, once the car is started, data then shows up on the SM!?!

What I'm thinking is that maybe the ECM has some internal issue that only surfaces once it is warm and heat soaked and with no data and ECM input during the start sequence that somehow the car is just allowing massive amounts of fuel through the injectors and flooding it out? Also, could the chip cause this kind of issue? I did put a new chip in with the injectors and this issue did start happening around that time. It is a TT chip burned for my setup.

Oh, I have already replaced the crank sensor and cam sensor chasing my tail on this. I have all green lights on my TR-6 ignition module. My TPS and IAC settings are in the recommended ranges. Fuel pressure in rail remains very solid after shutdown at around 41-42PSI, I am not bleeding pressure. I can hear fuel pump prime and shutoff after about 2 seconds with key turned half way. And -- the car runs great once it is started!

Anyone have this issue before or heard about it? I'm thinking next step is new ECM (even though current one is 6 months old) and different chip (even though it is brand new) to just to see what happens. What else should I be considering? What else is left to replace? Could a coolant sensor or oil pressure sensor cause a problem with the ECM like this?

Thanks, Dan
 
Whats the coolant sensor reporting? That could over fuel if its reading cold.

The scanmaster will show - - - - - - until the motor is started. Thats normal but you should still be able to scroll through all the other readings.

I doubt its the ecm or the chip. Stuck injector maybe. Also watch the alky light when your cranking. Make sure it's not spraying for some odd reason.

What injectors were in it before? Stock?
 
Whats the coolant sensor reporting? That could over fuel if its reading cold.

The scanmaster will show - - - - - - until the motor is started. Thats normal but you should still be able to scroll through all the other readings.

I doubt its the ecm or the chip. Stuck injector maybe. Also watch the alky light when your cranking. Make sure it's not spraying for some odd reason.

What injectors were in it before? Stock?
I think Rick is right about possible leaky injectors. They will cold start ok due to the need for extra fuel. Then when hot and that need is gone you see the trouble show up because they are dribbling fuel as it sits.

Were they bought new and a reputable brand?
 
Thanks for the responses and apologize for taking so long to get back on this.

Injectors that were in the car were stock, new ones are Mototron/Siemens 60 pound. I think they are widely used on GNs, sold by Cottons and a few other vendors we all work with. Leak down sounds like the obvious answer but there is no loss of fuel pressure in the rail once the car is turned off. It is rock solid for hours at 41-42 and if any fuel was seeping through an injector there would have to be some pressure loss -- wouldn't there? I did OHM the injectors too and they were all in the 12-14 range where they should be. Also, this hot re-start flooding issue mainly happens when trying to restart within a few minutes of shutdown so I would think if it was an injector it would really have to be stuck open wide and bleed alot of fuel to make the car flood so quickly?

I did put a new coolant sensor switch in and it is reading ambient temp when the car is started cold and when fully warmed up is in the 175-180 range. That seems normal to me so I think the ECM is getting good information on coolant temp.

I got a new ECM but have yet to put it in becaue I just don't think it will change anything. At this point the hot start problem is still there but seems to be becoming intermittent and sometimes now the car will start fine when hot?? I guess I just have to live with this gremlin until it fixes itself or one day the light bulb comes on and the real problem becomes obvious.

Last question, what do most people do with the fuel canister part of the emissions system? Leave it disconnected and cap the vacuum port it uses or do most people leave it connected?? I don't need to pass emissions testing and have already taken off my EGR valve. Just wondering if the fuel canister could cause any issues with starting?

Thanks, Dan
 
That's good that the injectors hold pressure. I missed that due to the long post, sorry. I think now maybe in the chips tune. Check with Eric at Turbo Tweak and see what he thinks.
 
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