MyE28.com

Hi all. I got my 1988 M5 to fire up for the first time in over a decade today. I rebuilt the top end after the PO overheated and abandoned the car [to me] as beyond what he wanted to get into. I replaced the entire cooling system too. Now, I have two issues I’m attacking.

The car will start and idle, but the moment I touch the throttle, it kills it. I’m wondering if I might have the pressure and return hoses swapped at the fuel rail. How do I know which of the hard lines coming through the firewall is the pressure, and which is the return line?

The other issue I have is that the temperature gauge is always at maximum. I can disconnect the wires at the sensors, and there is no change. Ignition on, gauge pegged. I have no clue. I have a new temperature sender, but I don’t think that’s the problem, since even disconnected, no change occurs at the gauge. I can disconnect the thermo time switch too. I wonder if this could be why I can’t throttle up?

Any advice will be greatly appreciated!

I think my HP fuel pump isn’t pumping. So I get a bit of gas up at the engine, but not enough to run the beast. I’ve ordered a replacement. By the way, since they stole the catalytic converter, I have no exhaust on the car (from the headers). The engine sounds amazing (loud and deep). Thanks all.

I did this. Bonehead me replaced both the lines near the firewall because I felt she was vaporlocking or heat soaking when really hot out. So, Replaced the lines not minding the orientation, added thermoshield braided sheathing to the said lines and installed. Went to start the Car and saw bubbles coming out near the FPR. Had a Duh moment... Swapped the lines and all was well. Car would not turnover though, so you likely have to play with your MAF/unplug it, check the CTS near the block and/or try to flash the codes from the DME if any exist. Because yours ran, you are likely looking at an AFM issue.

One of the other ways to tell which hard line is which is to blow into them. When you blow in the return, you will hear gurgle in the tank. Use a bic pen tube pushed into the rubber line.