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Hot Start Problem After Injectors Serviced
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Gauche1968
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PostPosted: Mon Jul 24, 2017 4:37 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

djkeev wrote:
Return line is after the pressure regulator.
The injectors are holding pressure and when you pinch the hose you are compressing the fuel by removing space for it, so the pressure rises.

Dave


Thanks, I took the injectors out and ran the leak tests anyway. They aren't leaking a single drop. So Injectors are ruled out.

I guess I am left with an AFM out of adjustment, ECU or a strange ignition problem?
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E1
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PostPosted: Tue Jul 25, 2017 12:32 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Sounds like you know what you're doing, but have you absolutely ruled out vapor lock?

Does your state's fuel blend change in summer?
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Gauche1968
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PostPosted: Tue Jul 25, 2017 7:39 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

E1 wrote:
Sounds like you know what you're doing, but have you absolutely ruled out vapor lock?

Does your state's fuel blend change in summer?


Symptoms are like vapor lock, but I have verified there is liquid fuel in the rails at the time of malfunction.

A few more updates:

Resistance in TEMP II wiring to the ECU plug is minimal. No more than 1 Ohm.

I did discover that the Hall Control Unit was testing below specs at the ECU plug. It was putting out only around 5 Volts (It was a cheap Meyle, made in China piece of junk). I replaced it with an old OEM unit, which passed the test, but the problem continues.

I also had trouble testing the secondary resistance on the coil. How do you do this with the multimeter? One lead on terminal 1, the other inside the center spark plug wire? Primary resistance was within specs, but on the very high end.

I am going to look at the starter and fuel pump wiring tomorrow. I hear the fuel pump running when the key is turned, but I suppose I need to verify what is happening at cranking. I don't expect to find any problems here, though.

Barring any discoveries, I am going to change the cap and rotor (but they aren't very old). If that is not the answer then someone is going to have to make sure the AFM mixture is in spec, I suppose.
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Howesight
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PostPosted: Wed Jul 26, 2017 8:20 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Here's a link to the Digifant Pro-training manual that can be very useful in diagnosing issues: http://www.vanagonauts.com/files/Digijet_FI.pdf

Thinking logically, considering the things that likely had to be done or disconnected when removing and re-installing your injectors, it is possible that you accidentally created a vacuum leak.

Hot starts do not have the enrichment that cold starts have, so vacuum leaks affect hot starts far more than cold starts. "Adjusting" the AFM is not a good start in diagnosing your problem. Remember that no matter how much you "adjust" the AFM, once the engine is at operating temperature, the Lambda system will always trim fuel mixture to the stoichiometric 14.7 : 1 ratio except at full throttle, when the "full" throttle switch allows the ECU to go to open loop mode.

It is possible that your injector O-rings are not sealing properly. Here are a few other common vacuum leak sources:

1. Throttle-body-to-AFM hose: they crack and the leak is only visible when you remove the hose, bend it and inspect it for cracks.
2. Loose clamp on throttle-body-to-AFM hose;
3. Breather tower diaphragm is perforated;
4. Valve cover gasket leaking permitting air leak into crankcase and then into intake manifold;
5. Leak in power brake vacuum line or loose clamp;
6. Crankcase- breather-to-intake manifold hose leaking or loose;
7. Power steering idle-up hose loose or compromised;
8. AC idle-up hose loose or compromised;
9. Auxiliary Air Regulator hose loose or compromised;
10. Intake-runner-to-plenum hoses loose or compromised.
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PostPosted: Wed Jul 26, 2017 9:56 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Howesight wrote:
Here's a link to the Digifant Pro-training manual that can be very useful in diagnosing issues: http://www.vanagonauts.com/files/Digijet_FI.pdf


That's the Digijet manual, not Digifant.
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PostPosted: Wed Jul 26, 2017 10:32 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Thanks, its a Digijet. Most vacuum leak areas have been addressed. But I'll keep checking...
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PostPosted: Wed Jul 26, 2017 11:10 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

That is a great list of high % vacuum leaks. I think someone should put that up in the engine sticky. I'm going down that list to see if my hesitation is one of these - thank you very much.
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PostPosted: Thu Jul 27, 2017 7:37 am    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Gauche1968 wrote:
Thanks, its a Digijet. Most vacuum leak areas have been addressed. But I'll keep checking...


I ended up sourcing a used redline smoke test machine.. I know my air/vacuum lines are not leaking under pressure. I did get a little smoke bubbling out of the dipstick tube seal, and then the oil filler tube. If you're around the SF Bay Area you're welcome to borrow it for testing! Otherwise it might be worth MacGyvering one of the home-made smokers to really know that all leaks are gone. It's also useful for checking exhaust leaks which can screw up the O2 sensor readings.

I would also add the throttle body gasket to the list.. they can become deformed and re-using them can introduce a small leak. If you don't have a fresh or uncreased gasket it can be difficult to get it back in the position that seals up completely again.
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PostPosted: Sat Aug 05, 2017 4:02 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Well, the problem is persisting. It is fairly consistent that when the hot start problem occurs, the battery and OXS lights come on. What is that telling me? Brand new alternator to starter wire from T3 on there, connections at the starter look good, connections inside the battery box look good, grounds have all been serviced, etc. There is one of the those variable voltage regulators on the alternator; its putting out about 14 volts.
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Wildthings
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PostPosted: Sat Aug 05, 2017 4:34 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Your battery light could be coming on because of the amount of cranking you are doing. It could thus be an effect of your starting problem and not a cause.

Have you messed with the mixture screw on your AFM? If it had previously been adjusted to account for low flowing out of spec injectors and now you have normal flow your mixture could be on the rich side at idle.

Note that the adjustment on the throttle body does not affect mixture, nor in general does opening the throttle as all air passing through the throttle body should have been metered by the AFM. Opening the throttle plate MIGHT cause the mixture to lean if the mixture screw on the AFM is way out of adjustment, but if properly adjusted no so much.
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PostPosted: Sat Aug 05, 2017 4:57 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Wildthings wrote:
Your battery light could be coming on because of the amount of cranking you are doing. It could thus be an effect of your starting problem and not a cause.

Have you messed with the mixture screw on your AFM? If it had previously been adjusted to account for low flowing out of spec injectors and now you have normal flow your mixture could be on the rich side at idle.

Note that the adjustment on the throttle body does not affect mixture, nor in general does opening the throttle as all air passing through the throttle body should have been metered by the AFM. Opening the throttle plate MIGHT cause the mixture to lean if the mixture screw on the AFM is way out of adjustment, but if properly adjusted no so much.


Hmm, interesting thought. I'll have to check how soon the Battery/OXS light comes on when the hot start problem occurs. I haven't messed with the mixture screw on the AFM, as touching that without the proper equipment can cause major issues--but it is clearly something I will need to address.
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PostPosted: Mon Aug 07, 2017 3:40 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Well, the problem is evolving. I can no longer say it is purely a hot start problem as today the symptoms emerged on the first start of the day with the battery and oxs lights coming on immediately (i.e. not after prolonged cranking). Still, the van will start and run seemingly normally after jamming on the throttle during cranking.

I checked the coil again and while I felt it passed resistance testing on the first go around, it did not pass this time; 1.2ohms primary resistance, 4300 ohms secondary resistance. Is this enough to rule the coil bad? Unfortunately, I get similar readings on all three coils I have here: The one on the other van, which is running fine with no starting problems and an old spare coil. Is this worth investigating further or are those resistance readings, although out of the Bentley range, nevertheless normal? The multimeter may have .1 or .2 ohms built in resistance.
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PostPosted: Mon Aug 07, 2017 4:01 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Have you replaced the electrical portion of you ignition switch?

No I didn't go back and read the entire thread to see what had been done. Wink
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PostPosted: Mon Aug 07, 2017 6:43 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Wildthings wrote:
Have you replaced the electrical portion of you ignition switch?

No I didn't go back and read the entire thread to see what had been done. Wink


Yeah, the ignition switch is not very old.
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PostPosted: Mon Aug 07, 2017 8:12 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Gauche1968 wrote:
Well, the problem is evolving. I can no longer say it is purely a hot start problem as today the symptoms emerged on the first start of the day with the battery and oxs lights coming on immediately (i.e. not after prolonged cranking). Still, the van will start and run seemingly normally after jamming on the throttle during cranking.

I checked the coil again and while I felt it passed resistance testing on the first go around, it did not pass this time; 1.2ohms primary resistance, 4300 ohms secondary resistance. Is this enough to rule the coil bad? Unfortunately, I get similar readings on all three coils I have here: The one on the other van, which is running fine with no starting problems and an old spare coil. Is this worth investigating further or are those resistance readings, although out of the Bentley range, nevertheless normal? The multimeter may have .1 or .2 ohms built in resistance.


Fresh batteries in the multimeter?
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PostPosted: Tue Aug 08, 2017 1:16 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

ohhorob wrote:
Gauche1968 wrote:
Well, the problem is evolving. I can no longer say it is purely a hot start problem as today the symptoms emerged on the first start of the day with the battery and oxs lights coming on immediately (i.e. not after prolonged cranking). Still, the van will start and run seemingly normally after jamming on the throttle during cranking.

I checked the coil again and while I felt it passed resistance testing on the first go around, it did not pass this time; 1.2ohms primary resistance, 4300 ohms secondary resistance. Is this enough to rule the coil bad? Unfortunately, I get similar readings on all three coils I have here: The one on the other van, which is running fine with no starting problems and an old spare coil. Is this worth investigating further or are those resistance readings, although out of the Bentley range, nevertheless normal? The multimeter may have .1 or .2 ohms built in resistance.


Fresh batteries in the multimeter?


Maybe, I'll check. Anyway, it's not starting at all today even when jamming the pedal. I can smell the gas flooding it out. I put the voltmeter on the coil positive side and the voltage fluctuates during cranking, but goes down to about 9 volts. Normal? Voltage during cranking at the battery and alternator do not go below 11 volts. I did have one hell of a time getting a new Bremi distributor cap to sit level on the distributor. I had to put the old Bosch cap back on. Very weird. I stupidly reversed the 1 and 2 plug wires on reinstall and started it, it ran for a second and died. I discovered my mistake and corrected it, but it will not start at all now. Going to have to give it a while to see if the flooded condition alleviates. I can see the Tach needle moving during cranking......

Bentley wants me to replace the coil. I am unconvinced though.
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PostPosted: Tue Aug 08, 2017 1:31 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Check your fuel pressure, maybe your FPR has gone south.
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PostPosted: Tue Aug 08, 2017 2:48 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Wildthings wrote:
Check your fuel pressure, maybe your FPR has gone south.


Thanks. Yeah, been that route. Fuel Pressure looks fine. Its holding residual pressure fairly well. It is slightly lower than pro training manual calls for after 10 minutes, but not by much. I have another FRP, I could try, but I am doubting its the problem. Pretty much stumped at this point....
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PostPosted: Tue Aug 08, 2017 2:53 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Gauche1968 wrote:
(FPR) slightly lower than pro training manual calls for after 10 minutes, but not by much. I have another FRP, I could try...


Probably not the problem then - I had one that held no residual pressure and it had no effect on running (discovered the failure while looking for something else).
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PostPosted: Tue Aug 08, 2017 3:24 pm    Post subject: Re: Hot Start Problem After Injectors Serviced Reply with quote

Ahwahnee wrote:
Gauche1968 wrote:
(FPR) slightly lower than pro training manual calls for after 10 minutes, but not by much. I have another FRP, I could try...


Probably not the problem then - I had one that held no residual pressure and it had no effect on running (discovered the failure while looking for something else).


Yeah, probably not. The fuel injectors aren't leaking, pulled them out and checked and they were just serviced by Mr. Injector who said they weren't leaking (although they had poor flow). If I understand correctly, the only way a failing FPR can cause flooding problems would be if it were leaking back through the vacuum line into the plenum?
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