Fuel check valve

[2fast]

Ok Guys I have a hard start problem when warm or hot so I thought I would try the Fuel check valve,I have a few questions.

Were is the old check valve does it have one?
Can I get this part at my local store or do I have to get it at BMA?
I sent BMA a email for a price and shipping cost to New Zealand.
What does this check valve do.
I had a look at http://www.bmwe34.net/e34main/trouble/535ihot_start.asp

Thanks

[Blitzkrieg Bob]

The fix kit from BMA is an inline valve that goes on the fuel line, under the access panel in the trunk

The valve keeps the fuel system pressurized so starts are a snap.

[Bill R.]

when that one fails you can use the inline as a replacement. The check valve keeps the line pressurized all the way from the fuel pump up to the injectors, this prevents vapor lock from ocurring since the boiling point of the fuel is much higher when its under 35 psi than at atmospheric.. So it serves 2 purposes , 1 to ensure that fuel is right at the injectors when you first crank it, and 2. to prevent vapor lock from occurring in the fuel line







Ok Guys I have a hard start problem when warm or hot so I thought I would try the Fuel check valve,I have a few questions.

Were is the old check valve does it have one?
Can I get this part at my local store or do I have to get it at BMA?
I sent BMA a email for a price and shipping cost to New Zealand.
What does this check valve do.
I had a look at http://www.bmwe34.net/e34main/trouble/535ihot_start.asp

Thanks

[2fast]

Thanks for great replies

Can I get this Fuel check valve from my local parts store or will they look at me funny when I ask for it.

[shogun]

http://www.bimmernut.com/%7Ebillr/images/bmwfuelpumpcheckvalve.jpg
I think the p/n is no longer up to date, latest one should be 16141179282.

Copy that. It might be and it is not the first time that local parts store will look at you funny when you ask for it.

[2fast]

I phoned BMW "sorry parts closed till monday"
So I phoned 4 part stores No No No No.
That number Shogun, can I use that at the BMW part store? 16141179282

[shogun]

That part number was given to me about 6 months ago from a guy in Germany. On 7er.com I do the tips and tricks corner and had posted the copy from BillR. So some people complained that they could not get the old p/n and someone mentioned this one. But I assume you can use any other check valve, as long as it lasts 3 bar.

[2fast]

Ok thank you :D

[2fast]

I Phoned BMW and the guy did not know what I was talking about,I said would a part number help he said "yes" so I gave it to him and he found it "Oh I have never seen one of those before Where did you get the part number" I reply from the internet (Thank's Shogun)
$92NZ 7-10day from germany.
BMA has them for $26USand$28US to deliver.
So they work out to be the same price all up so I will go with the stealer and will post when fitted.

[uscharalph]

"I Phoned BMW and the guy did not know what I was talking about,I said would a part number help he said "yes" so I gave it to him and he found it "Oh I have never seen one of those before Where did you get the part number" I reply from the internet (Thank's Shogun)"

We have our sources!

[2fast]

;)

[SRR2]

A nitpicky point for my edification if you don't mind: my experience with vapor lock was on cars built in the 50s and 60s with mechanical fuel pumps mounted on the engine that relied on air pressure in the tank to suck the fuel all the way to the pump. I had one problematic car in particular (I think it was a 62 Lincoln) that refused to run once run and parked on hot summer days. The fuel line was routed over one of the resonators and presumably the fuel just evaporated there and that was that, the car was immobilized. It sometimes took a couple of hours, and once in a while a jump start due to all the cranking, to get it going. I finally got fed up with that BS and put in a primitive electric diaphragm pump to replace the mechanical pump and the problem was essentially solved, though it was pretty funny listening to that diaphragm pump buzzing like crazy pulling vapor out of the line until the evaporating gas cooled the line enough to allow liquid to pass.

OK, so that bit of history said, how does a fuel system that uses a pusher pump in the tank ever get vapor locked? Doesn't seem possible to me. Check valve or not, once the pump runs and pressurizes the lines and rails to operating pressure, any vapor would immediately recondense, and 'locking' in the classic sense just can't happen.

[Bill R.]

into the top of the fuel pump... thats not the in line repair that they came up with.. In order to install this one you have to pull the pump out since its the original check valve.













http://www.bimmernut.com/%7Ebillr/images/bmwfuelpumpcheckvalve.jpg
I think the p/n is no longer up to date, latest one should be 16141179282.

Copy that. It might be and it is not the first time that local parts store will look at you funny when you ask for it.

[tim]

That 62 Lincoln had a one way system. All the pumped fuel was blown into the carbs, and any excess was held in the bowl. If the carbs flooded when warm, and the fuel line wasn't totally airtight, the fuel would back down into the pump and created a bubble in the line in front of the carb.. A check valve would fix that too.

On the BMW we have the recirculating type, where the pump goes to the rail and back again, so the whole line is pressurized. When you shut off the car and it's warm or you have leaky injectors, the fuel travels in both directions back to the tank, leaving a bubble of air on the fuel rail. As long as you can keep the gas up to the rail on the supply side of the system, it's fine. The return line is only a factor if it leaks.

So to answer your question, it's not vapor lock, and unlike the lincoln, if you keep cranking it will eventually start as long as the pump can get the system up to pressure.

[SRR2]

Tim, I understand the concept of vapor lock and know exactly how the fuel system in the Lincoln and the BMWs works. That wasn't the question, and for that matter, your diagnosis is wrong. Vaporization leading to "lock" occurs in areas of low pressure. Assuming that the fuel feed to the Lincoln's mechanical pump was normal, any bubble occuring between the fuel pump and the carb would simply have been pushed into the carb and vented into the intake the moment the float called for fuel. The vapor lock in the Lincoln was caused by 1) heating of the fuel line over the resonator, and 2) use of a suction type of fuel pump. Bad design combination.

The question, if you reread my post, was how come Bill R. calls the problem "vapor lock". The entire fuel system is pressurized, therefore I see no way for vapor to form in any part of the system that would 'lock' anything longer than a second or two that it takes for the pump to build full pressure. And in that case, I would hardly call it a lock. The Lincoln, when this problem occured, was "locked" in the sense that the engine was incapable of running. Now that's a LOCK, in my opinion.

As to "air on the fuel rail" Don't think so. There's no way for air to enter a properly working fuel system short of running out of gas. At most you'd have some fuel vapor, and that would recondense and/or recirculate back to the tank as soon as normal pressure is restored.

[tim]

Sorry, man. didn't mean to piss you off.

[DanDombrowski]

Im not sure if I'm pointing out the obvious here, but you can get vapor in the lines with the BMW system because the entire fuel system ISNT pressurized (at least when the fuel can drain back to the tank when the original check valve fails). Thats the whole point of the check valve, to keep it pressurized. I'm sorry if I'm misreading your question.

Now, would fuel vapor in the line lock it per say? I don't think so. Probably just people using the same terminology now as when they started using it.

[SRR2]

Right. We're in violent agreement. I wouldn't be a bit surprised to find vapor in the engine fuel rail if the check valve had failed. In fact, I'd be surprised if there weren't vapor there! My point, and I think we're on the same page, is that because the system is pressurized from the tank, it can't "lock" in the classic sense of the concept of "vapor lock" which is why I mentioned the Lincoln fiasco. Anyway, at worst, it will take a second or two to purge the vapor as the pump pushes enough fuel into the rail to recondense it and/or push it back into the tank.

I think this has been a productive argument. I bet there are at least one or two members who understand the role of the check valve a little better than they did before.

[Bill R.]

thinking that lock means to lock from starting and it doesn't. A vapor lock is strictly a bubble in a liquid line similar to the terminology air lock. Vapor locks on fuel lines with the old mechanical fuel pumps you referred to could occur while it was running causing the car to stall, they could occur after a hot soak as you mentioned, they frequently did occur at the suction fuel line since that was a low pressure area if it passed over a hot spot such as a resonator or exhaust pipe.. a large number of them vapor locked in the steel line coming from the mechanical pump on a v8 up to the carb after it was shut off and hot soaked. These vapor locks didn't always keep the car from starting and they frequently just required long cranking to get the car to start.... On the fuel injected cars the check valve fails , fuel boils in the lines at the engine and fuel rail, fuel is pushed back into the tank and a vapor lock in the line occurs, anybody that has worked on any fuel injected cars that this has happened too can tell you that it doesn't take just a second or 2 to clear, frequently you crank it for 20 or 30 seconds before it will start , acting very similar to the same vapor lock conditions on an old carburated car.











Right. We're in violent agreement. I wouldn't be a bit surprised to find vapor in the engine fuel rail if the check valve had failed. In fact, I'd be surprised if there weren't vapor there! My point, and I think we're on the same page, is that because the system is pressurized from the tank, it can't "lock" in the classic sense of the concept of "vapor lock" which is why I mentioned the Lincoln fiasco. Anyway, at worst, it will take a second or two to purge the vapor as the pump pushes enough fuel into the rail to recondense it and/or push it back into the tank.

I think this has been a productive argument. I bet there are at least one or two members who understand the role of the check valve a little better than they did before.

[SRR2]

I'm having trouble digesting the 20-30 seconds. Are you saying that it takes that long to purge the vapor? And if so, why is that? The volume delivery of the pump should be able to charge the entire fuel system in a lot less time than that, no? I don't have the spec of the fuel pump on hand, but imagine that it's at least a couple of GPM at reduced (i.e. vapor in the system) head pressure. With that assumption, a full charge into the fuel system should take a matter of a few seconds, certainly under 10. Now, I'll grant you that if there's vapor there, no fuel through the injectors, and the engine doesn't start right away, the ECU could get pretty upset and all sort of unusual things could happen causing that cranking time. I just can't wrap my head around that length of time just to purge vapor from the rails.

[tim]

The limiting factors on the amount of time to purge vapor is the vent rate on the vapor condensation tank, and the distance to which the fuel traveled back down the line. I suppose if you parked uphill, that could be as much as 10 feet of fuel line (1/2 my estimate of the loop). Or do I need another lesson?

[SRR2]

Are you talking about the vapor recovery canister? That shouldn't come into contact with liquid fuel. The fuel/vapor separator routes evaporated fuel from the tank to the canister, and when the engine is running the canister purge valve opens to vent the canister to the engine intake manifold. Looking at the E39 Bentley, most engines (except for the M62/TU) have straightforward plumbing. Fuel pump -> filter -> rail -> regulator -> return line -> tank. The V8s are simpler where the regulator is built into the filter and the return line runs from the filter back to the tank. There's only a single line to the rail on the engine. If there's vapor there, it's either goign to recondense when the pump runs, or it's going to be blown through the injectors as the fuel fills the rail.

I found a spec on volume delivery for the E30. It's .5 GPM at full pressure, measured from the regulator return line with the engine off. Delilvery at reduced pressures, like an empty line is going to be higher, but by how much I don't know. For sure, the delivery of E34 and E39 fuel pumps are going to be greater than that.

Just for purposes of discussion, let's assume that fuel line has 1/4" ID and there's, say, 15' of it. And the rail is 3/8" ID and 2'. And the fuel filter accounts for 3oz. That amounts to 8.8 in3, 2.6 in3, and 5.4 in3 respectively. .5 GPM is about 115 in3 /per minute, so the total volume to charge is 16.8 in3. At roughly 2 in3 per second, that's about 8 or so seconds to charge a completely empty system. Now, I realize that these aren't actual numbers, but I'm just looking for a good engineering estimate. In reality, the E34 and E39 pump outputs are going to be higher, and the system volume will probably be roughly the same, so the charge time will probably be less than this estimate.

[SRR2]

Oh, by the way, you're right about the car stalling even after it was running. It happened once while sitting in traffic on a really hot day. No a/c in that car either. That was the straw that broke the proverbial camel's back. It had the electric pump fitted the next day. It was surprising how often that pump actually did suck vapor on hot days even while driving. It was noisy and you could hear it buzzing fairly often when sitting at lights in town. The ambient temperature had to be below about 70 for it not to occasionally pull vapor.

No two ways about it, a pump at one end of the car trying to suck gas from the tank at the other end just isn't a good idea.

[Javier]

3 bar counterpressure, and only pushes fuel for a couple seconds at key turn before cranking, so if the check valve is bad, and fuel line dries back to the fuel tank and keep fuel vapor only, you have a nice time starting the engine.

Javier

[2fast]

Ok I have not ordered the part yet.
Here are my symptoms.
when cold car starts BANG!1 second.
When warm or hot may take 3-4 seconds embarrassing.........But not always
Sometimes it start fine when hot.

What do I do feller's.

[Bill R.]

number that shogun gave you will work if you pull the fuel pump out and replace the original check valve... It can also indicate a couple of other things such as leaking injectors which would also allow the fuel pressure to bleed down and would tend to make a hot engine flood so that it would take a little more cranking to start... If you hold the gas pedal all the way to the floor on a hot start does it start easier than if you give it no gas, If yes then that tends to indicate that its a leaking injector (1 or more) causing excess fuel in the manifold , causing a flooding condition which you have to crank until it clears, by holding the pedal to the floor it shuts the injectors off while cranking... this is the clear flood mode.... If holding the pedal to the floor doesn't help then its a bad check valve or a bad pressure regulator.., you can test to get a basic idea first by putting a fuel pressure gauge on it and cranking it to see how high the pressure goes and then letting it sit and see how quickly the pressure bleeds down... It should hold with virtually no leakdown for at least 1/2 hour min. IF it does leak down then you can pinch off the return line coming from the fuel pressure regulator back to the fuel tank and check again to see if it bleeds down, also remove the vacum line to the pressure regulator and see if any gas comes out of there. If these things make no difference then it narrows it down to fuel injectors leaking or check valve leaking.









Ok I have not ordered the part yet.
Here are my symptoms.
when cold car starts BANG!1 second.
When warm or hot may take 3-4 seconds embarrassing.........But not always
Sometimes it start fine when hot.

What do I do feller's.

[Alexlind123]

My car starts the same every time, that is it takes about 2-3 seconds to start no matter if it is cold warm or hot. Any idea what this could be caused by? Its not a real problem, its just that it seems as if it is putting a bit more strain on the starter than normal.

[2fast]

Having foot on the gas makes no difference.
So if I got this part and had to pull the fuel pump out, how easy would it be
to do?

[Javier]

should be a piece of cake.

Check valve (http://www.realoem.com/bmw/showparts.do?model=HD21&mospid=47383&btnr=16_0189&hg=16&fg=05)

Javier