1985 245dl 300K.

Friend borrowed car yesterday. He got about 70 miles then called and told me the car had just "stopped". Over the phone I ask him to check 25-30A fuse under the hood. He said it was blown. I told him where spare was. He put new fuse in and car would crank but still did not start. The new fuse did not blow. All other fuses were OK.

I drove out to where he was stranded. Checked that the spare fuse was OK. The car started immediately and ran smoothly.

It had been off for about 1.5 hours and engine was cool by that time.

I swapped cars and drove the Volvo 70 miles home without incident. The day was rather hot for northern california when the car failed with OAT probably was 95F.

Read the manual, haynes and searched brickboard. Both fuel pumps work when 4-6 jumper is placed. Main pump is a little noisy but pressure is good. Replaced wiring harness about 2 years ago and wiring under hood looks good. I had replaced 25A fuse holder with an in line, 50A weatherproof marine fuse holder. Fuse had simply blown. No corroded contacts, not evidence of overheating at holder.

Manual says that the 25A fuse serves the jetronic fuel injection system. I have no evidence that the FI system has failed.

Car runs fine now.

I am at a loss. Questions that come to mind.

What does the 25A fuse supply that requires that much amperage? The main fuel pump only has a 16A fuse. What can cause the 25A fuse to blow without evidence of bad wiring or a obvious short.

People talk about vapor lock, fuel pump relay failure, failed in tank pump, failed main pump. I have ruled out most of that except the possibility that the in tank pump has a loose hose and is sucking air in. As I said the main pump has a somewhat noisy whine but delivers good fuel flow to the rail. Could an overburded main fuel pump blow the 25A fuse? I don't see how.

Right now the car is running fine. I have not had an unexpected failure since replacing the wiring harness a couple of years ago.

I would appreciate any thoughts on the subject. I would prefer to fix the problem rather than find myself stranded.

"What does the 25A fuse supply that requires that much amperage?"
• FI ECU
• System relay
• AMM
• Idle Air Control (IAC) valve
• Injectors
• Fuel relay
• Main pump
• Tank pump
• O2 Sensor heater

"The main fuel pump only has a 16A fuse."
• If you mean fuse #6, it's not wired to anything on U.S. cars until the '91, when (as a 16 amp?) it replaces the 25 A blade fuse. Consider it a spare.

"What can cause the 25A fuse to blow without evidence of bad wiring or a obvious short."
• The exposed under car wiring to the O2 sensor heater (or a short there) are possibilities.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Yes, the fuel pump relay. It's the only part in the car with a date printed on it. Dated for a reason. I'm starting to replace them that have 2000-2001 on them, and I always have one on my shelf.

Check for corrosion at the 25 amp fuse holder and at the connection to the battery. Better yet replace the fuse holder with a water proof marine holder for $6 -8.

The fuel pump relay can be intermittent so replacing it is a good idea.


Dan