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Vacuum Leak I think

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1975 - 1993 240
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1990Volvo740
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Year and Model: 1990 Volvo 740 GL NT
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Vacuum Leak I think

Post by 1990Volvo740 »

Hello everyone

I changed only one of the hoses due to it's age and now the car has trouble starting when cold in the morning. I have to play with the acceleration pedal to get it to run but after that, not even 1 minute, the car will start at the turn of the key like normal.
I put the old hose back on the car and the same event occurs. What did I do wrong?
I've attached stills and a video in case there's an angle that will uncover something odd.
I did spray some carb chock cleaner into the intake manifold before attaching the new hose but that was it nothing else was touched.
Attachments
Hose Mov.mp4
(37.23 MiB) Downloaded 45 times
HS 01.jpg
HS 02.jpg
HS 03.jpg
HS 04.jpg
HS 05.jpg
HS 06 Ed.jpg

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matthew1
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Post by matthew1 »

That zip tie looks like it's crimping the hose. Maybe try without it, to test?
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volvolugnut
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Post by volvolugnut »

How well did the new hose fit the nipples at both ends? If they are loose, you may have a vacuum leak. Changing this hose may have moved and displaced other hoses. The hose to the flame trap under the intake manifold is hard to reach and can get hard and leak.
So it warm starts fine now after the cold start problem?
volvolugnut
The Fleet:
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1990Volvo740
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Post by 1990Volvo740 »

I changed the hose and the same issue happens in the morning. I'll check the rest of the hoses on Sunday.
The replacement hose in the video has a much smaller diameter and fits snug without clamps.
I am thinking that it might be a Cold Start valve issue even though I never touched the Cold Start Valve.
Are any of the hoses out of place in the Video?
Attachments
Hose Mov.mp4
(37.23 MiB) Downloaded 54 times

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volvolugnut
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Post by volvolugnut »

Check that the coolant temperature sensor wire connector is attached. It is below cylinder 3 on the head - near the area where you connected your new hose.
volvolugnut
The Fleet:
Volvo: 2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple Volvo parts cars.
Mercedes: 2001 E320, 1973 280, 1974 280C, 1989 300E, 1988 300TE, 1979 300TD, parts cars.
2009 Smart Passion
Ford: 1977 F350, 1964 F150 (2), 1938 Tudor Sedan
Farmall tractors: 1956 400 Diesel, 1946 A
And others.

1990Volvo740
Posts: 18
Joined: 10 August 2024
Year and Model: 1990 Volvo 740 GL NT
Location: Seattle
Been thanked: 1 time

Post by 1990Volvo740 »

volvolugnut wrote: 11 Aug 2024, 17:39 Check that the coolant temperature sensor wire connector is attached. It is below cylinder 3 on the head - near the area where you connected your new hose.
volvolugnut
Same issue on Sunday. I had to pump the accelerator slightly to get it to start but right after it reached idle speed, just 5 seconds and after I then turned the car off, I restarted the car and it started with just a turn of the key like before this issue.
What does the coolant temperature sensor have to do with the car starting at the turn of a key? I thought that part was only for sensing when the car was hot or overheating?
Does anyone have a diagram for the placement of the cooling hoses?

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volvolugnut
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Post by volvolugnut »

The basic electronics read the coolant temp and adjust the mixture for cold starting.
volvolugnut
The Fleet:
Volvo: 2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple Volvo parts cars.
Mercedes: 2001 E320, 1973 280, 1974 280C, 1989 300E, 1988 300TE, 1979 300TD, parts cars.
2009 Smart Passion
Ford: 1977 F350, 1964 F150 (2), 1938 Tudor Sedan
Farmall tractors: 1956 400 Diesel, 1946 A
And others.

1990Volvo740
Posts: 18
Joined: 10 August 2024
Year and Model: 1990 Volvo 740 GL NT
Location: Seattle
Been thanked: 1 time

Post by 1990Volvo740 »

volvolugnut wrote: 12 Aug 2024, 14:56 The basic electronics read the coolant temp and adjust the mixture for cold starting.
volvolugnut
Your reply was cryptic.
Is there a diagram that will show the location of the air fuel mix on this car?

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volvolugnut
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Post by volvolugnut »

From the Bentley Publishers Volvo 240 Service Manual (the 740 is very similar to the 240):
Fuel Injection system principles of operation -
"The coolant temperature sensor provides an engine temperature input that the ECU uses for enrichment during engine starting and warm-up.The cranking signal to the ECU is used to increase injector opening time and frequency for starting enrichment. In LH-2.4 and LH-3.1 systems, the cranking signal also triggers a cold start injector for added mixture enrichment."
volvolugnut
The Fleet:
Volvo: 2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple Volvo parts cars.
Mercedes: 2001 E320, 1973 280, 1974 280C, 1989 300E, 1988 300TE, 1979 300TD, parts cars.
2009 Smart Passion
Ford: 1977 F350, 1964 F150 (2), 1938 Tudor Sedan
Farmall tractors: 1956 400 Diesel, 1946 A
And others.

1990Volvo740
Posts: 18
Joined: 10 August 2024
Year and Model: 1990 Volvo 740 GL NT
Location: Seattle
Been thanked: 1 time

Post by 1990Volvo740 »

Could the Fuel pressure regulator also be the problem because it is controlled by the vacuum lines?
Is there a test for a faulty regulator?

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