| Author |
Message |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 71
Registered: 8-2001
| | Posted on Saturday, July 13, 2002 - 7:19 pm: | |
Greg,
If the check valve is internal, does one have to replace the whole fuel pump? If so, then what about putting in a fluid type check valve in line, at the fuel pump exit line?
Just a thought!!!!! |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 67
Registered: 8-2001
| | Posted on Saturday, July 13, 2002 - 2:05 pm: | |
Steve,
The Boxer service manual states to use the 400i manual for the fuel injection. It seems that there is only one service manual available for the Boxer, and this covers all three models. I have an English version but in the fuel section it only covers the carbs. I did recieve a copy of the 400i fuel manual with the BBi. The procedure is basically the same as that in the TR manual, with one major exception: In order to perform the tests one has to get the approriate fuel pump to run while in the "on" ignition position. In the TR this is done by using a jumper cable between 2 connections in the appropriate relay; while in the BBi, one disconects the air flow sensor connector, at the air flow sensor itself.
With the Bosch gauge that I have, it seems that a LOT of suttle systems of the fuel injection can be checked and diagnosed accurately.
David was right; without this gauge one can spend a lot of money going nowhere. I don't mind paying for quality test equipment, since they usually pay for themselves with the first use....especially on a Ferrari. |
Greg Rodgers (Joechristmas)
Member
Username: Joechristmas
Post Number: 387
Registered: 3-2001
| | Posted on Saturday, July 13, 2002 - 7:06 am: | |
I imagine the check valve is internal on your fuel pump as it is on my 83' QV. If you remove the fuel pump look down the front of it and see if you see a spring in there. If so then that is the check valve. Finding the external check valve that doesn't require banjo fittings isn't easy. I am not sure if the fuel pump/accumulator are on the same bracket like on the 308. It is probably your check valve as mine would not run on all 8 cyl. when warm sometimes. I also tried to turn the spring back in on the pump but it made it worse. I had to remove the air filter box and pressurize the system by hand to get it to start when warm. After I replaced the check valve it fires instantly when warm. HTHs. |
David Feinberg (Fastradio2)
Junior Member
Username: Fastradio2
Post Number: 89
Registered: 4-2002
| | Posted on Saturday, July 13, 2002 - 12:16 am: | |
Henry,
It has been a long time since I was intimately involved with K/KE fi systems....so I'll do my best from memory.
When cold, yes...the cold start injector(s) do play a primary role in getting the car started. The thermo-time switch determines how long the "extra" injectors will fire...and the control pressure will be low?? allowing the fuel distributors to provide more fuel at a small throttle opening i.e. fast idle condition....and cold enrichment.
When the engine is fully warmed up, or after an immediate hot re-start...the cold start circuit plays no role.
The problem, inherent with the K/KE systems has always been the problematic warm re-start, as residual fuel pressure is key here. Yes, the system does naturally bleed down, but ever so slowly. Once your get your pressure gauge hooked up, you should see the pressure drop slightly when the car is turned off and slowly drop to zero after many hours...However, if it drops to near zero, almost immediately, you'll have a rough time getting the car started...as you have, in essence a simulated cold start condition, but the cold start circuit will never engage, as the engine is warm.
Regards,
David
|
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 840
Registered: 1-2001
| | Posted on Saturday, July 13, 2002 - 12:01 am: | |
The TR WSM has a good description of how to test K-Jetronic "warm pressure when running" and "warm pressure after shutoff" (your 512BBi must be very similar). They give the spec in a way that allows some pressure loss with time but makes sure that the rate of loss is slow enough that things will become "cold" again so that you should never have the combination of low (or zero) pressure and very warm coolant during restart --
minimum pressure after 10 minutes: 2.7 bar
minimum pressure after 20 minutes: 2.6 bar
The warm pressure when running is in the 2.7 to 3.9 bar range (depending on vacuum applied) and the primary supply pressure should be 5.0 to 5.6 bar.
They also mention that a problem in retaining pressure after shutoff can be caused either by the aforementioned primary pressure circuit problems (leaky fuel pump check valve, leaky injector, etc.) or more subtle problems in the control pressure circuit (but that's probably less likely). Anyway, I just wanted to mention that the TR WSM might be a good K-Jetronic reference for you if there isn't something more 512BBi specific.
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Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 66
Registered: 8-2001
| | Posted on Friday, July 12, 2002 - 11:21 pm: | |
David,
How long would these residual pressures hold up? Wouldn't there be some loss in pressure over time? Theoretically they whould last a long time, but realistically I can't imagine that being the case. If so, then how does the car start so easily after sitting for a month?....is it due to the cold start injectors?
Henry |
David Feinberg (Fastradio2)
Junior Member
Username: Fastradio2
Post Number: 87
Registered: 4-2002
| | Posted on Friday, July 12, 2002 - 10:37 pm: | |
Henry,
That's the gauge!Hopefully the adapter fittings for the 308 are the same for the BB...
As to the gauge hook up...too many years have passed to describe from memory. If you've got any Bosch FI books or 308 FI manuals, there should be some info on the procedure....or someone on the board who has done this test recently would be more qualified to walk you thru the steps to install...(Sorry).
The "accumulator" is really a pressure damper, to smooth out the pump pulses...hence delivering a constant flow of fuel. It does not effect residual pressures.
Regards,
David |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 62
Registered: 8-2001
| | Posted on Friday, July 12, 2002 - 10:33 pm: | |
David,
Would you believe.....I have this gauge, with a bypass valve.....just found it in the basement. It is a Bosch gauge for K-Jetronic. It is part #KDJE-P 100/2. The gauge reads 1-10 Bar. I bought it years ago, when I had a 308, but I never had to use it. Your note reminded me of it.
The bypass valve has an "A" line....one with a hose open to hook up, and the other end (180 degrees apart) going to the gage. At 90 degrees there is a "B" line, with a hose attached just open at it's end, ready to hook up to something. At 180 degrees from the B line is an adjustable knob. Where would I hook this up?
If the check valve holds the pressure, then what is the purpose of the accumulator?
Thanks to all for your help. |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 61
Registered: 8-2001
| | Posted on Friday, July 12, 2002 - 10:27 pm: | |
David,
Would you believe.....I have this gage, with a bypass valve.....just found it in the basement. It is a Bosch gage for K-Jetronic. It is part #KDJE-P 100/2. The gage reads 1-10 Bar. I bought it years ago, when I had a 308, but I never had to use it. Your note reminded me of it.
The bypass valve has an "A" line....one open to hook up, and the other end going to the gage. At 90 degrees there is a "B" line, just open. At 180 degrees from the B line is an adjustable knob. Where would I hook this up?
If the check valve holds the pressure, then what is the purpose of the accumulator?
Thanks to all for your help. |
David Feinberg (Fastradio2)
Junior Member
Username: Fastradio2
Post Number: 85
Registered: 4-2002
| | Posted on Friday, July 12, 2002 - 9:58 pm: | |
Henry,
Steve is right on the money here with the injection being all about pressures. Typically, a K/KE injected vehicle which starts well cold, but has difficulty starting hot after sitting an hour, or so...is due to the residual pressure in the system bleeding down too quickly. The most common cause is the check valve in the fuel pump(s). As Ed stated, depending on the pump used, the check valve may, or may not be a replaceable part separate from the pump itself.
As to quicky and accurately determining the problem, a Bosch or equivelent fuel pressure gauge with bypass valve body is required. Without such a tool, you can throw alot of money into the wind quickly.
Any competent shop (VW/Audi/Porsche)should have these gauges, and know how to test the system on your car...as it is not unique to Ferrari.
It has been a long time since I had to do these tests, but memory serves me that warm pressure is approx. 1.4-1.7 bar...and immediately after shut-off the pressure will drop by .2-.4 bar. What you don't want to happen is to have the pressure drop to near zero immediately when the vehicle is turned off. Note that this test can be done on both banks for comparison purposes...as separate pumps, etc. are used.
Fuel system residual pressures is your starting point...
David |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 60
Registered: 8-2001
| | Posted on Friday, July 12, 2002 - 8:49 pm: | |
Thank you Steve and Ed,
I'm interested in investigating this fuel pump check valve, since all injectors, and accumulator where replaced less than 1000 miles ago.
Is the check valve part of the fuel pump.....and how would I test for it?
Thanks again |
Steve Magnusson (91tr)
Member
Username: 91tr
Post Number: 839
Registered: 1-2001
| | Posted on Friday, July 12, 2002 - 8:33 pm: | |
(I'm starting to hate guessing at these things, but) It sounds like you've got one bank losing fuel pressure slowly sometimes after shutoff (leaky injector, bad accumulator, leaky fuel pump check valve, etc.) making warm restart difficult for that bank (by feathering, you're running on the good bank until the bad bank eventually develops enough fuel pressure to be active). The "problem" isn't as noticeable cold because some fuel will get delivered to the bad bank on cold start by the cold-start valve. Or -- I could be completely wrong! But I do know that proper K-Jetronic operation is all about pressure control so you really need to make pressure measurements to diagnosis -- good luck... |
Edward Gault (Irfgt)
Intermediate Member
Username: Irfgt
Post Number: 1571
Registered: 2-2001
| | Posted on Friday, July 12, 2002 - 8:26 pm: | |
Sounds like the check valve in the fuel pump is not holding pressure. It is possible that there is some other internal leakage point in the Injection system but the fuel pump is the most likely area. Some of these pumps have a replaceable check valve and some don't. |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 58
Registered: 8-2001
| | Posted on Friday, July 12, 2002 - 8:13 pm: | |
I should ad that this doesn't happen all the time, but the frequency of the problem is slowly increasing. |
Henryk (Henryk)
Junior Member
Username: Henryk
Post Number: 57
Registered: 8-2001
| | Posted on Friday, July 12, 2002 - 6:51 pm: | |
My 83 BBi starts fine when cold. However, when I have to make a stop for about an hour, with the engine warm, it doesn't want to start easily. It seems that not all cylinders are starting at once. I need to feather the throttle to prevent it from dying out. Once it starts it runs fine.
Any suggestions?
Thanks |