M25 Breakdown

[oneohtwo]

Had a bit of an odd moment on the M25 last Friday. Was in slow moving traffic when all of a sudden throttle became unresponsive and started stuttering. Pulled over to the left and it seemed to settle down and was ok just at a steady speed or slow revving. The traffic came to a stop and seemed likely to sit there a while so I switched off, but then it wouldn't restart. Kept turning over but not firing.

Pushed it over to the hard shoulder and was waiting for 2 hours for assistance and on the off-chance tried again and the engine fired up and I got to the next services with the engine apparently running fine. Didn't want to risk the same again so got towed.

Could this be fuel pump related or something else? (Didn't want to hijack the fuel pump thread down there!) That's my initial thought... temperature all seemed fine and normal, low 90s. Oil all fine. And how can I diagnose it as fuel pump definitively short of swapping it over and seeing if it happens again?

[a_riot]

Could be a fuel pump or a crank sensor issue from your description of it. The crank sensor can get moody when hot, and without it working correctly the car will crank but won't start. But then a few minutes later it will run just fine. It's typically an inexpensive part and easy to replace.

It could also be a failing fuel pump, bad fuel pump relay or fuel delivery issue. I had an issue with the wiring from the fuel pump to the pump connector and had to resolder those connections due to a bad solder joint. Pierburg pumps, which I assume your is, usually don't have intermittent problems though, they either work or they don't from my experience.

Some diagnostics you can do is listen to the pump and make sure its always running at the same speed, not cutting out at times or slowing down, check the fuel screen at the bottom of the pump and the fuel filter to see if you have some kind of gunk in there blocking things up. If you have a Power Probe, you can send 12v directly to the pump connector and listen to the pump run to see how it sounds. Some say you can check the resistance across the +/- and see what you get, although I'm not totally confident that is always that useful. Normally resistance is low, under 10 ohms iirc, but I've seen different values on pumps that work fine.

I'm currently pulling my pumps to swap the old rubber hoses to new nylon hoses from the pump to the top hat. Many Corrados have the factory hoses replaced with standard fuel hose, which is not rated for submersion in fuel, and so deteriorate and leak over time. Here's what mine looked like.


End of hose delaminating...


Rubber hose turning into black goop...


Imprint of clamp on hose...


Completed with nylon hoses...

[oneohtwo]

Some good info there thanks. Will try and do some investigations this weekend.

That pipe looks nasty, don't particularly want that getting in your fuel!

[1200 bandit]

Got 2.0 16 v had some thing similar,replace the battery,Also found wiring to the throttle body snapped
Removed the fuel pump from inside the tank ,found bits of foam inside the fuel tank,(replace the the 2 fuel pumps)
Once the repairs was carried out running ok
Has not broken down for 12 mouths which is quite amazing

[a_riot]

No worries, hope it helps. The last time I changed the fuel filter, I was surprised at how black the crap that came out of it was. I can't be sure but I suspect its from the black goop that eventually melts off the hoses that was the culprit. I'm going to do the same thing to my other Corrado this weekend so both will get clean gas.