warm start problem

[jbiebl]

Is there a way to tell whether it's the fuel accumulator or the fuel pump that could be causing a warm restart problem? Filter was changed last year; FA ???

82 SC - stored/not driven since last fall. I had it happen maybe 2x all last year, but it has happened every time (~6x) this spring.

thanks
jb

[boyt911sc]

Originally Posted by jbiebl

Is there a way to tell whether it's the fuel accumulator or the fuel pump that could be causing a warm restart problem? Filter was changed last year; FA ???

82 SC - stored/not driven since last fall. I had it happen maybe 2x all last year, but it has happened every time (~6x) this spring.

thanks
jb

JB,

All you need is hook up a fuel pressure gauge and measure the fuel pressures (residual, control, and system pressures). The residual pressure will tell you if is low or not. Two (2) common culprits for low residual pressure problem are defective FA and FP check valve. And the WUR's pressures (cold & warm) will tell the you its condition. While the system pressure will indicate FP's ability to deliver sufficient fuel (assuming that the fuel distributor is good).

If you don't have a fuel pressure gauge kit to use, simply remove the FA (fuel accumulator) and do a bench test. At this point, I would guess you have a three (3) port FA. Remove all the residual fuel in the FA.

Test I: Fill the upper chamber (FA) with fuel. If the fuel drips from the bottom port, the diaphragm is ruptured or broken.

Test II: Use compressed air to pressurized the upper chamber and observed passage of air at the bottom drain.

There is also another test that you could do with the FA in-situ but needs to run the fuel pump. At this time, I would reserve this procedure until you are familiar with the safety operation of pressurized fuel. There are many knowledgeable guys in this forum to assist you. Keep us posted.

Tony

[jbiebl]

Many Thanks

will try #1 and/or 2 manyana, and relay results.

Again, thanks
jb

[jbiebl]

The FA holds fuel perfectly well; no leaks.

Is that a definitive result, or should I do the air pressure test also?

Is there a way to check the fuel pump and/or one way valve?

You are correct that I do not have a fuel pressure gauge kit.

thanks again
jb

[Vincent Hill]

I "HAD" this kind of a problem on my 1976 and eventually put in a Large 924 accumulator. Also I "Added" an extra Fuel Pump Check valve along with new Injectors. I feel it was MOSTLY that the Fuel Accumulator was not large enough to do the job. The 82 has a large accumulator so you may want to add another Check Valve to the Fuel Pump.

[boyt911sc]

Originally Posted by jbiebl

The FA holds fuel perfectly well; no leaks.

Is that a definitive result, or should I do the air pressure test also?

Is there a way to check the fuel pump and/or one way valve?

You are correct that I do not have a fuel pressure gauge kit.

thanks again
jb

JB,

If the FA holds fuel without any sign of fuel leak then the diaphragm is still OK. No need to do the air test. At this point, I'll consider the FA passes the test under atmospheric pressure. During actual operation there is fuel pressure working against the diaphragm. Next is the FP check valve. Since you don't have a FI pressure gauge will skip this test for the meantime.

Measure the flow rate of your FP. Recommended flow rate is about 1 liter per 30 seconds or 2 liters per min. Take multiple measurements and take the average. How do you do this?

By running the FP without the engine running. Remove the fuel pump relay and connect terminal #87a & #30 (ignition @ON position). Use a suitable jumper wire with in-line fuse. Measure the flow rate at the connection before the FA. This could be done conveniently by a person but I would suggest that you seek an assistant to help you do the test.

If FP passes the test, then I'll bet my money on the FP check valve to be the culprit. A residual test will confirm whether the check valve is leaking or not. If you want to test the FP check valve, remove it and do similar test like you did with FA. But it will entail more work for you. Like draining the fuel tank, FP removal and re-installation, and so forth. Keep us posted.

Tony

[Vincent Hill]

I thought there was a fuel line to the Fuel punp that could be clamped off? I used 2 pieces of flat 1/8 inch thick aluminum plates about 1 inch square and a pair of Vice Grips to clamp the fuel line and then removed the pump and change the one way valve

[jbiebl]

I did the FP test 3x: approx (min) 1.5L/30 sec. was the average.

So: unless I can change the valve in the FP, or add a new, secondary one-way valve to the fuel line near the pump, it sounds as if I may as well pull the FP out, and do the last check on the one-way valve at that point for assurance before ordering a new FP.

If I can add/or change the one-way valve w/o replacing the FP, is there such an animal?

Does the vise grip idea work on the fuel line? Safely?

thanks
jb

[sparkle84]

Maybe Tony would know if it's possible to do the following. Immediately after shutting the engine off, pinch off the return line. Wait awhile & remove clamp & try starting. If it fires right up then the check valve is bad. Or could it still involve the FA?

[boyt911sc]

Originally Posted by sparkle84

Maybe Tony would know if it's possible to do the following. Immediately after shutting the engine off, pinch off the return line. Wait awhile & remove clamp & try starting. If it fires right up then the check valve is bad. Or could it still involve the FA?

Sparkle,

Pinching the return line has nothing to do with the operation of the FP check valve. The check valve is used to prevent the backward flow of fuel in the delivery line (FP to FA section) to the tank during shutdown. Why would pinching the return line necessary in your opinion? Or maybe you meant the fuel hose between the tank and FP? Please advise. Thanks.

Tony

[T77911S]

the fuel line is hard, dont crimp it. just change the check valve. the FP does not need to come out. changing the check valve is not that big a deal. you will get some fuel from the line and with the front jacked up, this will help. but if i remember, not much gets past the pump.

[jbiebl]

Thanks

I can't find a fuel line check valve listed on Pelican; am I just missing it?

Not much room around the FP to work in, is there?

thanks
jb

[T77911S]

yea, sometimes i have a hard time finding simple things too. select fuel pumps then scroll pages, you should see them.

[jbiebl]

Oh. Ooops. Sorry.

Ouch!

thanks again
jb

[T77911S]

not your fault. like i said, i have tried to find things but i have to select something related and then scroll pages

[Vincent Hill]

Originally Posted by sparkle84

Maybe Tony would know if it's possible to do the following. Immediately after shutting the engine off, pinch off the return line. Wait awhile & remove clamp & try starting. If it fires right up then the check valve is bad. Or could it still involve the FA?

Great test! 20 years ago, it would have been nice to have been able toi use the internet like nowadays! We really struggled back then and now it is Sooo easy! (Like this place)

[boyt911sc]

Originally Posted by Vincent Hill

Great test! 20 years ago, it would have been nice to have been able toi use the internet like nowadays! We really struggled back then and now it is Sooo easy! (Like this place)

Vincent,

It is definitely a lot easier today to communicate and exchange ideas via the internet. The digital cameras also contribute for something difficult to describe in plain simple words. While most contributors' intentions are to help find a solution to the problem/s, error or mistake do happen unexpectedly.

The 'Great test!' you happened to like is flawed!!!! Go back and re-read until you find what's questionable with the test procedure. The pinching should be done before the FP and not after the FP to test the check valve's operating condition. Sparkle had the right concept and I honestly believed he was referring to the fuel line before the FP and not the return line. I also get into this kind of trouble more than I wanted to. We all make mistakes.

Tony

[jbiebl]

Parts ordered, and I'll pass on the results after they install themselves.

thanks everybody
jb

[Gunter]

Originally Posted by jbiebl

Parts ordered, and I'll pass on the results after they install themselves.

thanks everybody
jb

What parts did you order?

Some thoughts:

I recently replaced the old pump with a new one and found that both types had internal check valves with an M12 x 1.5 mm nipple for the banjo fitting.

You don't know what type of fuel pump you have.
You may have a type that has an internal check valve.
Adding an external check valve has the pump working against 2 valves; not good.
For the time and effort involved, consider a new FP especially if it's really old or you may find yourself doing the same work in the near future.

SC's can have Bosch or Pierburg pumps, with or without internal/external check valves.

Hopefully, you'll have a newer Bosch pump with external check valve and a banjo fitting for the M12 x 1.5 mm. However, the nipple may just be a nipple or it may contain the check valve. They look very similar.

Replace the short hose from tank to pump with a new one. 12 mm or 1/2" x ~3 inches.

Fuel will leak and drip or even gush.
Fire Extinguisher close by!

I recommend draining the tank to minimize leakage and accidents.

[jbiebl]

Yup. I think I misunderstood that I could just replace the check valve. Here's a pic of my FP, and it looks suspiciously like it may have an internal check valve. (Can anybody tell for sure?).

I have put everything back together until the parts come, and am driving it daily to lower the fuel.

If the pump and the FA seem to be working fine, it would seem to be a defective check valve (somewhere-internal or external), so would adding an external check valve cause a pressure/other problem?

You're right; I probably should order the fuel line.

thanks to all
jb