fejjj

Drove my car over to a friends house with my son to photograph his 89 Speedster. He only lives about 2 miles from me. I parked the car in his driveway which is on an incline. Went to start the car after sitting for 1/2 hour and it fired up then immediately stalled. It kept trying to start but would immediately stall. It seemed like it wasn't getting enough fuel.

Rolled it down the driveway and pulled out so the car was now on a slight decline. After a few tries over the course of 20 mins (it continued to fire but not run) it finally started. Let it idle for about 20 mins to recharge the battery then took it for a run.

It was running pig rich under boost (mid 10's). Only drove it for about 10 mins. Shut it off and restarted and it immediately stalled. Tried to restart it and fired right up.

Another thing I noticed that when letting off the gas, it normally returns to 14+ AFR fairly quickly but now it is taking about twice as long.

After reading several threads and Clarks garage, I am thinking it is either the FPR or fuel pump check valve.

Any help would be appreciated.

Tom M'Guinn

Could be lots of things, but I'd be inclined to check the AFM and connector (or MAF -- whatever is delivering air flow info to pin 7 of the DME). These cars will usually start off the maps and then promptly die when the AFM signal is way out of whack (or shorted or open). Try wiggling the connector when it starts/dies. If you're handy with a multimeter, check the voltage on pin 7 with everything connected when it starts... Should be in the .5 to .7 volt range +/-...

Could be lots of other things of course...but fuel pump check valve wouldn't be on my list for those symptoms.

fejjj

Tom,

I have an M tune and I checked the connectors and all is good and tight.

Would a loose MAF connection also cause a Rich condition under boost?

89 951
M tune/80lb injectors
3 Bar FPR
K27/8
3" turbo back exhaust
Rogue ECU
E85
Lart fuel lines
LR Vac line kit

Tom M'Guinn

I don't have any experience with m-tune, but you might double check the ground to the MAF.

fejjj

Anyone else?

refresh951

A faulting fuel pump check valve would not cause the car to run rich.

fejjj

Hi Shawn,

Do you think it could be the FPR then?

The 2 things that are happening are the starting issue and the rich condition under boost.

If not the FPR then where else should I be looking?

fejjj

Ok more information.

While boosting the car stumbles and backfires at 5200 rpm.

Any ideas?

Symptoms:

1. Starts and immediately stalls
2. Running rich
3. 5200 RPM cut and backfire (sometimes)
4. Only cuts while under load
5. Warm engine idle AFR 14.2, cruising 3rd gear 3k RPM 12.0, full boost 10-10.5

refresh951

What plugs, gap? Check rotor, cap, and wires. pull the plugs and have a look at them. Could also be a sticking injector.

fejjj

Plugs now are BPR6ES with whatever gap they come with.

Cap, rotor and wires all replaced 2 years 7k miles ago.

When I went to pull car from storage 4 weeks ago it kept trying to start, and did a couple of times then would immediately stall. It had BPR7ES plugs then. I drove to the parts store and all they had were the 6's so I put them in and the car started right up.

I did notice the 5.2k cut last fall just before I put the car away for the winter.

fejjj

Ok. Just went to start it and it started and ran for 3 seconds. Tried again and it fires but won't start. 3rd try cranks but no fire. There are fuel spatterings on the ground behind the exhaust.

This has more or less been the pattern when it doesn't start and continue to run.

Tom M'Guinn

Could be lots of things, so you'll have to dig in a little to figure it out. I'd start by diagnosing why it's not starting and idling, and the high-speed stumble may go away as a result. (If not, then I'd start looking at ignition parts like Shawn said...).

When the car starts up and runs for a second before dying, that often points to an air-fuel ratio that's way out of whack. That can be caused by the engine management system commanding the wrong fuel (due to a bad sensor, harness or dme) or a defective mechanical part (bad FPR or vacuum line to it, huge vacuum leak elsewhere, bad injectors, etc.). I'd start checking all the air intake couplers closely for leaks. And make sure the idle screw isn't turned in completely, and that the air filter isn't a solid block of dirt. Then check for a good strong spark at the plugs, and test the fuel pressure when it starts up. If that checks out, then I'd measure the MAF voltage on pin 7 of the DME, and confirm the TPS switch/pot signals are getting to the DME properly. If that checks out, then I'd check for proper pulsing from the injectors. Chances are one of those tests will send you down the path to a solution -- no guarantees of course -- but always wise to test the basics first.

fejjj

Tom,

After talking with Joshua, I have decided to start with the FPR and Fuel dampener.

He also suggested that the Air intake temp sensor may be the culprit.

I appreciate your help and suggestions very much!

With the M tune, where is the Intake Air Temp sensor located and does anyone know the part number?

Rogue_Ant

Sorry, not air intake, I meant coolant temp sensor.

fejjj

Ok thanks!

BTW...it does it on both cold and warm starts.