454XL EFI stopped suddenly, ideas?

Hi guys

One of my 454's was running at cruising speed around 4000rpm on the weekend. Had been running fine for 30 mins, suddenly there was a cough and the engine stalled.

We were able to restart later in afternoon after it had cooled off by increasing throttle enough and also priming the fuel system.

At idle it ran roughly but when we increased the revs it started cutting out the cylinders slowly until the engine stalled again.

Mechanic has had a look and advises fuel pressure as 20psi on both engine but the problem one drops away as revs are increased whereas the other engine stays steady at 20psi.

Mechanic reckon the fuel pump is faulty and has to take engine out to work on it. Has anybody seen anything like this and should he be doing other trouble shooting before we pull the boat from water and start removing engines.

Crusader engines are practically unknown here in Australia and our mechanic is only used to Mercruiser on the same Chevy block.

Thanks for any help you can offer.

Shouldn't have to pull the engine to work on the fuel pump unless it is installed in a shoebox.

Most fuel pumps are controlled using engine oil pressure - no oil pressure, no B+ to keep the pump running. The earlier ones use an oil pressure switch to keep the fuel pump running. The newer ones use an oil pressure sensor feeding the computer and the computer controls the fuel pump.

There have been many instances of the switch failing so I'd encourage the mech to check that first. Also, tell him the control of the fuel pump is similar to the Merc approach; the parts are usually physically different.

May also be the fuel pressure regulator. Should be able to hook it up to the computer to find out.

If you have a Silverton 360 there is no need to pull the motor, you can get to the pump if you want to. Tell him to pretend it's a Mercruiser. Troubleshooting and repair are the same I don't care what color it is. Check all the filters, including the Oberg. Check the anti-siphon valve. If the fuel pressure issue persists, you're probably looking at a fuel pump.

Thanks for your help guys. I've got the manual on it's way to me here in Australia, once it arrives we should be able to run some diagnostics and work out what is going on.

Whilst waiting we're replacing all the cockpit upholstery and trim plus we'll do her yearly clean etc.

I'll let you know what we discover!