'79 244. When the key is turned to the on position, the fuel pump does not run. When the key is turned to start, it cranks but does not run (presumably due to lack of fuel) when the key is turned from start back to run, the fuel pump primes and the car can then be started normally. It starts every time I need it to, but I don't know if this is will progress into not starting at all. Previous owner said that a mechanic said that it could be the ignition switch. Would that make sense? Is there anything that you would inspect first?

If your fuel relay is the original "k-jet relay" you should hear the pumps buzz for a short second when you turn the key to KP-II for the first time. All later versions of the relay I've seen also do this, but I can't tell you for certain every aftermarket replacement made in the past 40 years will.

This "priming" is not there for the function of priming. Never was. It is just a byproduct behavior of a circuit that looks for ignition pulses to allow fuel to be pumped, and stop that pumping when they go missing for more than a second. However, priming is what it has been called by inference. The fuel system in your car, and that in all RWD Volvo cars does not need priming to ensure quick starting.

But .. this buzz before cranking turned out to be a great indicator to mechanics that the pumps are operating, so in the later cars, after many years lacking that behavior in LH1.0, LH2.0, and LH2.2, the firmware for LH2.4 re-introduced it. Not for quicker starts, but for the diagnostic convenience. Your relay was introduced in 1978 as John noted. Before that, the airflow meter operated a switch that gated fuel only after cranking introduced manifold vacuum -- again, no possibility the fuel lines would be "primed."

What you really need to maintain this 79's fuel system is a fuel pressure gauge. With a gauge, you can learn if the pump's check valve is maintaining rest pressure stored in the accumulator. That is necessary for re-starting the car hot, otherwise you will experience fuel injection vapor lock as the pressure of heated fuel/vapor pushes the fuel fluid out of the roller pump under your car.

You will use that pressure gauge to measure the performance of the CPR or WUR I mentioned in my response to your greetings thread. And once you get the system working as it should, you'll see that "priming" isn't necessary; that full pressure from the main pump is available before the cranking achieves two revolutions. If that one second buzz were necessary, your owner's manual would suggest you buzz the pumps once before turning the key to crank. LOL

Here are some links to get you advice from some folks experienced with k-jet.

TurboBricks brand K-jet Fuel Pressure Test Equipment

Building the Best K-jet Fuel Pressure Tester: What Would You Pick?

And one I put together if you can get a store-bought gauge:

Using the K-jet Fuel Pressure Test Kit



Enlarged relay picture

And if you're into the why of things and their guts, K-jet relay internals

And the changes made since 78 include the fusing of the tank pump at the main panel (#5)





If you're gonna keep the car, build or get a fuel pressure test set. My unsolicited but enthusiastic advice.


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Art Benstein near Baltimore

What’s the best thing about England?
I don’t know, but its flag is a big plus!

Then I stand corrected on the so called priming issue. I have only noticed this behavior in my departed '89 wagon. Heard it every time. Expected it.

But in two K-Jet cars with Stribel relays I simply do not recall this. Not that I doubt you, Art.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Don, you shook my confidence enough by saying you don't remember this priming. Because, I realized I didn't really remember it either, so I thought I'd refresh what I was so thoroughly confident about by checking it in my car.

I know now why I don't remember hearing it. My bad habit is to start the car first and click the seat belt later. The raucous seat belt buzzer drowns out any buzz from the pump motors.

I buckled the belt under me and held in the door switch. Yup, there's the buzz.

So I figured I'd try the few k-jet relays I have in my junk collection, all of them Stribel with Volvo numbers. First one, a Volvo 3523639 with a what looks like a 98 date code on the cover, behaved just as Cerulean describes: no initial buzz, and a half-second run after any brief cranking stops. So, I'm totally wrong, claiming all the k-jet relays cycle on power-up. Apparently just some of them do. The original relay, Volvo 1348600 and another Volvo 1235337 provide a power-up buzz from the pumps, but this later version 3523639 refuses. I'll have to look into the circuit to see what they did to "fix" this.

TLDR for OP: Your relay, tho "primeless" is not a problem.
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Art Benstein near Baltimore

Is it true ants never get sick?
I don’t know, but they sure as hell have anty-bodies.

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Art Benstein near Baltimore

“The only true wisdom is in knowing you know nothing.” -Socrates

Art's definitive analysis!! Took only 40+ years to discover this. Something we would otherwise never have known. There's nothing like doubting your aging recollections to force you to fully investigate an issue. Happens to me more and more these days.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

This fuel system wiring diagram is for '78 but I think it may be the same for 79 also.

Most likely the fuel pump check valve, which can be replaced.

Volvo part number 1326899.



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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

If that were the case, wouldn't the pump still prime or would this prevent it from priming?

This system, assuming we are talking about K-Jetronic which was OE for US market cars in '79, should not prime. The fuel pump will not run until the starter motor is engaged. You can see this in the diagram provided by 81242DLB21FCA, "Engine stalled (ignition on but engine not running)". Although there are some differences between '78 and '79, this part is true for both, in fact all, K-Jet cars.

If your car was actually priming with the ignition only on, I suppose it is possible that someone before you may have monkeyed with the electrics to provide line pressure before starting. The only reason to do this would be if the check valve failed.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

How can I test if this is the problem?

First I would like to know something. In your original post you state, "...when the key is turned from start back to run, the fuel pump primes..."

Are you actually hearing the pump run or is this an assumption that since the car will now start it has therefore, "primed?"


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

If there is delayed starting that requires multiple or extensive cranking then Bulletproof Don is likely correct about the check valve. To diagnose, you would check for loss of residual line pressure at the fuel rail after the engine has been sitting awhile, such as overnight, but if the check valve is really fouled or stuck then the pressure will quickly drop after stopping. If you had a Schrader valve on the fuel rail you could easily use a cheap tire gauge to check for pressure dropping, but you don't and will need to open a line up, ideally to insert a fuel pressure gauge, but just to check for any kind of residual fuel pressure should suffice in your case. If it's been sitting overnight or for a couple of days there will only be a momentary trickle. Be careful of spilled gas.

Another easy thing you can try for an initial no start is to reach underneath and give the fuel pump a large number of good solid raps with a hammer. If it now starts then there is a dead spot in the motor where having to first crank the starter motor one or more times to give it a voltage surge nudges it past the dead spot and gets it going. That might better correlate with your description of the symptoms. The in-tank pre-pump can't provide enough pressure on its own. It's not uncommon to have both a failing fuel pump issue and a check valve issue. People often don't notice loss of pressure if it just requires a bit of extra cranking.

I believe others are correct, the K-Jet system does not try running the pump as soon as you switch the ignition on. It must see the engine turning over, such as when cranking and providing spark. I don't recall that LH 2.0 even did a pump prime, it wasn't until LH 2.4 that has a CPS. Some people do try to run the FP relay directly off the ignition switch when they are having problems, but that mostly applies to some of the problematic early LH 2.4 ECUs.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

A sure sign that the check valve has failed is if when you disconnect the fuel line from it, fuel continually drips or flows out through the valve from the tank. It's also an easy $20 fix to replace the valve if you want to rule it out. Make sure you have containers ready to catch spilled fuel, and be a bit gentle with the connector and line. A new Bosch valve will come with a new washer.