'98 M3 OBD1 conversion hard starting

[clovold]

Hey all,

I just finished the OBD1 conversion on my '98 M3. Added 24lb injectors and a euro hfm. 506 ecu with Turner chip specific to the injectors & euro hfm.

I reused the OBD2 fuel rail and kept the OBD2 fuel pressure regulator and a Turner Y cable to split the temp sensor output.

It idles rock solid and runs like a scalded ape once I get it started.

The problem is that it is very hard to start. After turning over for a few seconds it will sputter a bit but not start. A lot like an old carbureted car that is flooded. It takes two or three times of hitting the starter for 5 seconds before it catches.

I'm pretty sure that all the sensors are connected properly, and I used new crank, cam, and oxygen sensors.

I may have reversed the fuel l ines, though. I didn't label them. Could that cause it? Could it be the OBD2 FPR?

Ideas anyone?

[soulrebel]

Either your lacking spark or fuel, check both.

[Corky325]

If you reversed the fuel lines, then the regulator will not regulate properly. I would say that would be your problem. Otherwise, it is possible you have bad injectors. They could be dumping in to much fuel during start.

[clovold]

After MUCH diagnoses I have learned a few things:

It's flooding out. I pulled the plugs after trying to start a while and they were all wet. Not just one or two, but all. Sounds like the coolant sensor, right? I tested the coolant sensor value at the ecu and both air and water temp values were in line (2.1k ohms). I even tried swapping the gauge and ecu coolant temp connectors but it didn't help. I also tried reversing the fuel lines but, as I suspected, it didn't do anything. It looks like the fuel rail is just one all the way through, so reversing the lines doesn't matter.

I even tried swapping out the ECU with a known good one borrowed from a guy who used to race E36s. It started the same with his ecu.

Fuel pressure is 3.5 bar while cranking, 3.0 bar at idle once it starts.

The car has new knock sensors, can sensor, crank sensor, and oxygen sensor.

What else is left? The only thing I can think is that it may have something to do with the remaining parts of the OBD2 fuel delivery system. The 3/2 diverter valve has an electrical connection that isn't used in the OBD1 setup. What does this do? If it drops fuel pressure during startup or something then that could cause it.

I didn't open the engine up during this conversion, and it was running great before. I just did an OBD1 conversion with 24 lb injectors and a euro hfm.

Thanks,

Craig L.

[325icintn]

Could it be the OBD2 FPR?
Fuel Lines – The fuel delivery setup is significantly different between OBD2 and OBD1. The OBD2 fuel rail has both fuel lines attaching in the rear near the firewall and the fuel pressure regulator is located forward of the fuel filter under the driver side of the car. The OBD1 fuel rail has the supply line on the front of the rail and the return line on the back of the rail near the fire wall. In addition, the OBD1 fuel pressure regulator is on the fuel rail itself next to the return line. You must use the OBD1 fuel rail for the conversion, which will require modification to the fuel lines. You will need to remove the OBD2 fuel pressure regulator from the undercarriage of the car and route new 8mm fuel lines to the OBD1 fuel rail. There is a pair of hard lines mounted to the chassis between the OBD2 fuel filter and engine bay. Simply bridge the gap left by the removal of the OBD2 fuel pressure regulator with new fuel line and connect the feed from the fuel filter to the front of the OBD1 fuel rail and the return line from the back of the fuel rail to the return line under the car. You will also need to connect the OBD1 fuel pressure regulator vacuum line to the one-way valve on the bottom of the OBD1 intake manifold. The connection is on the back corner of the manifold closest to the firewall.

OBD1 conversion (http://www.m3forum.net/m3forum/showthread.php?p=1750853#post1750853)

Now that your obd1, the next step is turbo.

[tjn182]

Hey all,

The problem is that it is very hard to start. After turning over for a few seconds it will sputter a bit but not start. A lot like an old carbureted car that is flooded. It takes two or three times of hitting the starter for 5 seconds before it catches.



Mine does the same thing 25% of my start-ups. Strangely, it is easier to start when it's doing this if I hold the accelerator pedal flat on the floor.

[clovold]

Reversing the fuel lines on the fuel rail doesn't matter, it's a straight-through open system.

You DON'T need to use and OBD1 fuel rail or fuel pressure regulator. I didn't and it works fine. you just have to add two metal plates to allow the OBD2 fuel rail to hold onto the M50 manifold, since the bolts don't line up. And add a couple washers to space it down properly. I just updated the OBD1 thread over there to reflect that information.

The solution was EWS!!!! I cut the EWS wire and the she starts perfect every time!

Even though I was using a 506 ECU it was still an issue, even though people say that it isn't!!

Why did it let the car start at all with EWS interfering? I have no idea. But cutting the wire solved the problem!

[325icintn]

The FPR must be downstream of the injectors; that's what matters. It sounds like you have the lines correct.

EWS should have prevented the car from starting, so I agree with your that your solution does not make sense. Hopefully it will continue to work.

[polishracing95]

i had the same problem and it stumped me for a while... i swapped the fuel lines and it fired up on the first try... its easy to do and if that doesnt do it at least its one less thing to look at

[neptronix]

This is a common problem with OBD1 manifold swaps, and any modification that involves reducing air intake velocity and increasing air intake volume
( cold air intake, manifold, throttle body, etc. )

I've seen threads here where people are trying to figure this out and replacing
every friggin' part and come to no resolution.. esp. when it comes to OBD1 manifold swaps. I bet the HFM bit exacerbates the problem even more.

I noticed this issue crop up a little when i put a CAI on my 328is.
No longer starts like a champ :(

IMO it's probably normal..

But good luck.


Hey all,

I just finished the OBD1 conversion on my '98 M3. Added 24lb injectors and a euro hfm. 506 ecu with Turner chip specific to the injectors & euro hfm.

I reused the OBD2 fuel rail and kept the OBD2 fuel pressure regulator and a Turner Y cable to split the temp sensor output.

It idles rock solid and runs like a scalded ape once I get it started.

The problem is that it is very hard to start. After turning over for a few seconds it will sputter a bit but not start. A lot like an old carbureted car that is flooded. It takes two or three times of hitting the starter for 5 seconds before it catches.

I'm pretty sure that all the sensors are connected properly, and I used new crank, cam, and oxygen sensors.

I may have reversed the fuel l ines, though. I didn't label them. Could that cause it? Could it be the OBD2 FPR?

Ideas anyone?

[JoeDellio]

What about once it starts and runs, can you turn it off and start it right back up?