I just purchased a '76 264DL that has a rebuilt B21 engine with the K-Jet fuel injection. It looks like I need a new fuel pump. When I turn the key, the "buzz" from the fuel pump is constant and not just a short buzz like on my other ones.

Since I have a B21 engine, do I need the fuel pump designed for the B21 or do I just get the Bosch one for the '76 Volvo's? Were they different? Thanks

You should ask your mechanic who is excellent by the way and knows these Bosh systems very well. He can supply you with a pump that pays no mind to power.

>When I turn the key, the "buzz" from the fuel pump is constant and not just a short buzz like on my other ones.

On a '76 you shouldn't be hearing anything. The fuel control is different than the later cars. There should be a 2-pin plug connected to the airflow unit, which has a contact that only lets the pumps run when cranking/running airflow is sensed.

Maybe that airflow plug is off/loose, or someone may have hacked around with the fuel control wiring.

If you ever do need a pump, it's not the same as '80 and later. May be hard to find too. IPD has an adapted '80-'83 version for #318.00!!!

Without the Model YEAR in your Subject line, you're likely to get some hasty responses that won't apply to your old-timer.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Thanks Bruce

On my '75 164E, it uses an electric fuel pump (just replaced it..$350 Bosch). My 164 runs flawlessly. When I turn the key on, there is a short "buzz", maybe not even 2 seconds, and then it stops. I was told that was something like a priming injection of fuel.

The one on the '76 operates the same way, it just has a constant buzz and it does not stop. My mechanic told me that means it is ready to go, if it hasn't already.

I did find a NOS Bosch one on Ebay, one that fits the car and does not have to be adapted for $155. After doing some checking, I found the part number on my old pump and made the match on Ebay

My mechanic told me that means it is ready to go, if it hasn't already.

Sorry, but IMO your mechanic does not have a clue about the correct operation of your fuel system. I have owned and maintained a '76 240.

What you have is an inoperative Safety Feature.

All Bosch systems are designed so that no fuel is pumped to an engine that is not running (except for that brief "buzz" you mentioned). This is to prevent starting or feeding a fire in case of an accident, where the driver might be unable to turn the key OFF.

Glad you found a pump, just in case you ever need one. Hope your luck with a mechanic is as good.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

I'm not sure I was clear about this. You acknowledge that there is a brief buzz with these fuel pumps and in your first reply you state that you should not hear any noise at all.

My '75 pump has that initial brief buzzing sound when you turn the key on and then it stops. The problem that I am having with the current pump on the B21 engine is that it does not stop buzzing. I turn the key to the on position and it constantly buzzes, an obviously malfunctioning fuel pump.

My mechanic is excellent and he does understand the Bosch fuel injection system very well. And from experience with my old pump on my 164e, when it did this exact same thing, it was a faulty pump and a new one corrected the problem. As we all know, these old Volvo's are pretty quirky and sometimes develop a mind of their own :)

I turn the key to the on position and it constantly buzzes, an obviously malfunctioning fuel pump.

Any pump runs (buzzes?) as long as it gets voltage from it's fuel control circuitry. The fact that your '76 control circuit is erroneously sending voltage to run the pump continuously with the engine off doesn't mean the pump is malfunctioning at all. It's just doing what it's "told".

I can't speak to how your '75 164 works. I can only describe what your '76 should do, based on my experience, Bosch manuals, and wiring diagrams. It's true that some later K-jet cars do buzz the pumps briefly, due to their type of fuel relay. But your car does not use that type of relay.

However, after reviewing the wiring (it's been quite some time), I can see where there could be a very brief voltage pulse to the pump when turning the Key On. In your case, I'd guess that you may have a bad Main FI relay, or open safety contacts on the airflow meter. Either one would allow constant voltage to the pump with the Key On.

My intent was to save you from needless pump expense — and to let you know about a flawed Safety circuit that your mechanic is content to overlook. It seems you've already decided the pump needs replacing, and aren't concerned about the Safety issue, so I'll ring off here.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.