Hi. My 1990 745 sometimes stalls at red lights and is difficult to restart--or won't restart for 15 minutes. When this happens I have fuel pressure (fuel squirts from the Schrader valve on the manifold. Good, regular spark from the plugs, and battery voltage at the injectors. Today I got a 1-4-3 knock sensor code. I wonder if the knock sensor could cause the engine to die and not restart until after cool down? I worked on these cars for many years, but not on ones this old and with this high mileage. Thanks for any insight. May 22, 2019. Paul Smith. Raleigh, N.C.

 

usually warm start problems are related to fuel pressure (low fuel pressure can lead to vapor lock), air intake leaks (ie vacuum lines/air boot cracks, idle air valve), leaky injectors or the engine temp sensor. I'd probably start by looking for any signs of a leaky injector (puff of black smoke on start up? wet plug?) and then consider measuring fuel pressure at the rail before starting and with the engine running, You can also measure the resistance of the temp sensor (google for a resistance by temp chart).

 

I'd change the Crankshaft Position Sensor; sounds like it heats up, then once cool the car starts.

 

OK. Thanks for that. I put an electric fuel pressure gauge on the dash. It's reading around 40 psi--on my third fuel pump.

 

OK. Thanks. That's probably my best alternative. Wiggling the sensor harness didn't help when it went into stall mode.

 

For mine it would stall almost every time I slowed down or pulled up to to stop at red light turned out it was the alternator, but I would make sure to clean the MAF sensor electrical connections as mine were showing some green corrosive build up and will cause issues.

 

OK. Thanks for the help. I don't have a MAF--it uses a MAP. I've never seen a MAP go bad. I was about to try a new flywheel sensor, but I have spark when it dies and won't restart. I'm thinking of monitoring the drivers on the injectors to see if the computer is not grounding the injectors. Any more advice appreciated!

 

if you have a MAP, that means you have a Regina injection system... I've never even seen one of those (I don't think they sold them here in California).

 

Crank Position Sensor! 10 dollars and 10 minute job to change one.

 

I wouldn't put a $10 CPS. Pay the $40, get an OEM, some parts are too important to go cheap!

 

Probably not, due to emissions restrictions. It was similar to Bosch LH 2.2, but used a map sensor instead of a AMM. The ignition system was called "Rex I)

 

Agree on the quality issue. But, I have strong, rhythmic spark when it won't restart, so flywheel sensor must be ok.

 

Okay. I have to ask here. I am trying to change my crankshaft position sensor. Above, someone said $10 part, ten minute job, or something of the sort.
I did not get the $10 part, but opted for the slightly more expensive alternative. However, I am finding it impossible to feel my way around the back of the engine to unbolt the old sensor, let alone, figure out how to bolt in the new one. Definitely not a 10 minute job unless I am missing something.
BTW, 93 240 B230F.
Any help here with the back end of the sensor?

 

Find the connector on the fire wall, should be easy, probably has some black ties holding it along with some other wires, the washer lines, etc, should be in the center more or less, may be 1/3 of the way closer to the driver's side, follow it and it should go down into the top front the bell housing, where it connects to the engine. A 10mm bolt holds it in place, use an extension to get to it. Once the bolt's out, reach down there and wiggle the sensor out. Use a flashlight, it's easier to see it from the passenger side.

 

Yeah - it isn't the easiest job due to the location of the sensor. I have used a 10 mm socket on a flex shaft with a long extension to loosen the bolt. I have also had troubles before where once the bolt was removed the sensor was stuck in the hole due to moisture that got into the sensor causing the internals to rust and expanding the plastic. A lot of wiggling was necessary to get it loose while trying not to break it off. All of this is made harder by the location. Take your time, keep at it and you can get it out. I don't ever remember it being a 10 min job for myself. Invented new cuss words along the way.

 

It kinda depends... shouldn't but it does! I've removed many, the ones from rusty areas are usually harder, as is all work done on rusty cars. The CPS is easier to get to if you stand on something if you are on the short side...

 

An overdue update:
Got it done. My wife helped. She was able to get it rethreaded and I got it tightened. Good team work.
Also, one thing I found in a video that helped. Maybe this goes without saying, but in my case, everything needs to be said: Take out the rear spark plug cable. That made a world of difference.
Thanks for the advice and encouragement. I'm learning more everyday. Most days, anyway.