Hi friends.
Newbie there, greetings from the Czech Republic.
After 2 years of work my XJS 5.3, MY 1988, H&E USAroadster version is on the road (previous ownercompletely cooked engine, all was blue). Slowly solve problems that occur.
One is is ''knocking'' fuel pump (old pumpmade the same, I bought new, but problem persist). Ignitionis off, on, no matter. From the pump I hear: knock, knock, ______, knock, knock knock,,____, knock, etc.
I cannot find why. Some ideas, please ?
Thanks for the answers.

 

It could ne cavitation because the feed to it is partially blocked. I seem to recall the H&E has a dual tank system with the lower tank feeding the upper tank via a small intank pump, and the top tank feeding the engine. I have never seen an H&E though, so this is only an idea.


Maybe worth checking that the lines between the two tanks are clear and the extra pump is working properly? Also, if you disconnect the feed at the injector rail input, does the pump still knock?
greg

 

Hi Greg.
Thanks for the answer. Yes, You have right. Two tanks, two pumps. Lower repumped fuel to the top.
Both tanks was out form the car, was cleaned and pulling back. I have new hoses, new fuel filter and upper pump. Every hose is passable. Knocking is only when engine is not running.
I will change injectors on the rail, so I try then disconnect the feed. And then we'll see.
Roman

 

The fuel pumps should only run for a few seconds when the ignition is on, and then the ECU turns them off if the engine is not started. If this only happens when the engine is NOT running, how long does the knocking go on?
Greg

 

Constantly.never stops.

 

It looks like someone has changed something from OEM spec. The ECU should (on OEM spec cars) stop the pump after about 3 seconds if no engine starting signal is received from the ignition amp. I highly doubt that H&E would have altered this safety feature.


The WoOz, Grant Francis, is the expert on this area, and I am sure he will be along to suggest something when the sun aligns with South Australia.


Worth checking if the knock is coming from the engine bay, just could, I suppose, be the fuel pressure regulator hammering as it is being pressurised but no fuel being used.


If you disconnect the fuel line before the A bank regulator and turn the ignition to start the pumps, does it still knock?


Greg

 

After disconecting fuel line knocking is out. When connect back, knocking was cca 5 second from regulator AND pump, then only pump.

 

Therefore your problem is that the pump is running continuously when the engine is not, so you need to properly wire the pump circuit to the ECU to fix this. The knock is "hammer" in the fluid fuel circuit caused by the regulator opening and shutting somewhat violently to control the pressure.


You can bypass the A bank (inlet side) regulator completely, by the way


Greg

 

Hi Greg.
Thanks. It is good direction.
Some remarks.
I tried change ECU (I have the same number in the drawer) : LUCAS, 16 CU, 84526D, DAC4585. It is remastered from UK, so I think that have nothing common with H&E. Knocking is there always.
I tried change bank A fuel regulator (I have old, but was on the running engine), knocking is there always.
But when I change this regulator, I forgot depressure system. But there was no pressure in the rail, only spilled some gas. It is not right, isn´t it ?
So can be bad some of injector (leaking) or bank B regulator ? The pressure in the rail is missing and ECU say to the pump : work, no pressure. Or it is bad idea ? Thanks for Your time. Roman.

 

Here is what I would do in your place:

• Forget the fuel pressure disappearing, it has nothing to do with the knocking. If the car is running nicely fuel pressure and injectors are OK
• The fact that the fuel pump is running all the time, ignition on, engine not firing, is DANGEROUS. The pump has been hot wired by someone. Return it to OEM spec. This means getting to understand the correct wiring and reinstating it. This is NOT an ECU problem. The pump should only run for a few seconds ignition on, then the ECU stops it. Get the wiring right and it will stop.
• If you are going to do anything to the engine bay fuel parts, remove the A bank regulator completely and connect the pump feed directly to the rail; and then change the B bank regulator for a new one (the b bank regulator runs a different pressure to the A bank one). The hammering is I think, (impossible to be sure without being there to listen) being caused by the fuel pressure regulator snapping open and shut violently and causing a fluid "hammer" in the system. The B bank regulator is the one that pressurises the fuel rail, so that is the one that matters.

Greg

 

1. All right.
2. Problem is, that the pump is NOT running all the time. Only knocking. When I switch battery ON, for 3 second I hear noise from pump, and pump input wire (+) is on the value 12 V (same for the lower pump). Then pin 87 on the pump relay go to the value 3 V, pumps are silent and every seems all right. Only knocking is there. I made video, You can see and hear it here :
roman-mg | Pump_knocking ? rajce.net
3. Bank B has new (not old, but working) regulator, I am waiting new for bank A next week. I understand the principle, which You wrote.


Then I try make direct connection to the bank A. But I would like to know who is knocking, when the pump is not working .
Roman

 

The speakers on my computer are not great and my ears are middle aged and questionable but....

To me the sound is not fluid. It sounds electrical. Like a solenoid or relay.

I'd be curious to disconnect the fuel line from the pump and see how it affected the sound. I'd want to see if relieving the line pressure remove the noise. If not then I would look at the electrical circuit.

Mark

 

Hi Mark.
Thanks for reply.
Yes, it sounds as relay etc. but when I put my hand on pump, I FEEL the sound. When the fuel line is not connected in regulator, knocking is out.
Tomorrow I disconect fuel line direct from the pump. and +12V wire.

 

I am totally confused.

I thought you said that:
1) The pump was running all the time the ignition was on, and
2) The knocking goes on all the time the pump is running, and
3) That the knocking stops when the pump was running but the fuel line was disconnected from the A bank regulator

Now, are you saying that:
a) the pump stops after 3 seconds ignition on, and
b) the knocking does NOT happen when the pump is running, and
c) the knocking happens AFTER the pump stops ?

Finally, it would be worth checking that the fuel return line from B bank back to the tanks is clear and unblocked by blowing some air through it, fuel filler cap OPEN. The video you posted sounded a bit like a fluid decompressing by "popping" as pressure is being released in jumps. ONE way to test for this is to switch on the system, ask a friend to switch it off while you simultaneously UNDO the A bank fuel line going into the regulator FROM the pump. If the knocking stops once the pressure is released (try the test a few times to be sure) then that seems to indicate that fluid depressurisation is the cause. If it the test does indicate it, also check if the noise happens if the fuel filler cap is left OPEN.




Greg

 

Hi Greg,
Very sorry, "constantly, never stop" I wrote in context "knocking".
So (maybe final, but I have some problem with technical terms in English) :
After connecting battery (I have a switch) :
1. Fuel pump is working (noise) for three seconds. Then stop.
2. Knocking :
a) engine is not running and
b) fuel line is connected to A regulator
3. No knocking:
a) engine is running or
b) engine is not running and fuel line A is disconnected
It is better ?


Fuel return line B to tank is clear (tested with compressor).


All other I try later or tomorrow.


Thanks Roman

 

So new stage.
Pump relay have two 87 output (parallel).
First for the fuel pump.
Second for - 45 second timer, both oxygens sensors.
When second is connected to relay slot, fuel pump is knocking.
When is disconnected from the slot, no knocking.
I think, that something (45 sec. timer, oxygens sensors, or whatever "on the road" to second 87 output) do it.
I try disconnect 45 sec.timer and then (if will be no knocking) I have to go over wires.

 

Good find. As you say, check the wiring, as it is possible, the relay itself may be faulty, it may be easiest to change that first.
Greg

 

Relay was the first thing. It is new.
And both regulators.
45 second timer - after disconnecting knocking live with me further
I am going to solenoids.

 

I have a solution.
New relay.
Take 87 output to pump as a new relay input, take somewhere 12V ignition ON as a power output.
Power output make as a new output to the pump. Switching with old 87 relay pump output.
But this is the easy way. Nothing for the man

 

End of the game.
Power 12V to oxygen sensors connectors had short-circuit to ground (somewhere on the road from second pin 87 relay in the boot). So my cuurrent between minus pole of disconnected battery (ground) and body was 2.5A !!!
When all was connected, then to the pump relay (87 pin) went voltage from sensors shorted wires (from parallel 87 pin) and relay switch on, switch off. Knock, knock, knock.
Solution.
New wires from boot pump relay (secondary 87 pin) to sensors. Body ground is really ground. Battery is not discharging. Everything is all right.
Now, the only "knocking" that I hear in my car, is a amazing song from the player