Car Keeps Cranking But Won't Start
02-19-2019, 01:58 AM
#1
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Car Keeps Cranking But Won't Start
I have an 03 E500. It's in great shape & well-maintain. Yesterday, I started the car, it ran for ~ 30 sec then shut itself off. I've tried to re-start a few times but it kept cranking but wouldn't turn over. I've replaced the crankshaft position sensor & the fuel pump relay but those weren't it. I did some more troubleshooting by measuring the voltage at the fuel pump's connector & noticed it does switch to 12V for a few seconds when the key is turned to the ON position. I understand this quick turn on is used to prime the system but I didn't hear the pump working at all. Btw, I applied a constant 12V directly to the fuel pump using an external battery & at time, I was able to get the pump started & got the car running but as soon as I removed the 12V, the car would shut off again once all the fuel in the line is consumed. What do you think, a faulty fuel pump or something is wrong w/ the electronic circuitry?
02-19-2019, 10:23 AM
#2
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1922 Ford Model T / no OBD
You are hacking computerized car who suppose to be troubleshoot with proper scanner.
What sounds like long way you went, could be diagnosed in just seconds with scanner.
Choosing scanner is not easy, but my iCarsoft MBII does a lot on those cars. and $150 is not bad price.
What sounds like long way you went, could be diagnosed in just seconds with scanner.
Choosing scanner is not easy, but my iCarsoft MBII does a lot on those cars. and $150 is not bad price.
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Adil Al Ismaili (04-30-2020)
02-19-2019, 11:04 AM
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1922 Ford Model T / no OBD
You should be able to read fuel pressure?
If not - HF sells traditional gauges as low as $19.
If not - HF sells traditional gauges as low as $19.
02-19-2019, 12:35 PM
#5
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Fuel pressure is fine once I got it going w/ a constant 12V to the pump. The problem I'm currently having is not being able to get the pump activated when it should be. There must be another relay somewhere beside the fuel pump relay in the trunk. Does anyone have a schematic of the fuel system so I can take a look & see how it's wired? Thanks.
02-19-2019, 02:22 PM
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'71 Pinto
Here’s wiring diagram no additional relay, check ground. If fine pull pump and filter (left side) check connections above & below.
02-19-2019, 03:09 PM
#7
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I couldn't jump start the pump w/ a constant 12V every time so it could be due to grounding or the pump is on its way out. I'll check the ground. If it's fine then I'll buy a new OEM pump. I'll report back on the finding. Thanks.
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02-19-2019, 03:31 PM
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1922 Ford Model T / no OBD
Not the way I would troubleshoot, but good luck with your idea,.
02-19-2019, 11:31 PM
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2006 E350
I had a similar problem a few months back but mines turned out to the be the relay for the fuel pump. Have you checked the fuse? If I remember correctly it was in the trunk close to the relay.
02-20-2019, 10:10 AM
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'71 Pinto
As shown in post 6 wiring diagram f4 (15A) @ rear SAM.
02-20-2019, 03:48 PM
#11
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I was hoping it's either the fuse, the relay or a lose ground but they're all good. I did some more troubleshooting last night & narrowed it down to the fuel pump. I even used a dummy load to simulate the pump to test the relay's control signal & the 12V line which are used to turn on & power the pump. Since the fuel filter is inside the fuel sending unit, I went ahead & ordered both OEM parts so I can sleep better at night. It'll take a few days to arrive so I should be back in business next week. Thanks everyone.
02-20-2019, 11:13 PM
#12
I was hoping it's either the fuse, the relay or a lose ground but they're all good. I did some more troubleshooting last night & narrowed it down to the fuel pump. I even used a dummy load to simulate the pump to test the relay's control signal & the 12V line which are used to turn on & power the pump. Since the fuel filter is inside the fuel sending unit, I went ahead & ordered both OEM parts so I can sleep better at night. It'll take a few days to arrive so I should be back in business next week. Thanks everyone.
Last edited by Pennywise1975; 02-20-2019 at 11:23 PM.
02-21-2019, 12:11 AM
#13
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If you're getting fuel pressure & the car fired up then the pump is working so your issue isn't the same as mine. Did you get a reading of the fuel pressure & what's it? How was the car running before? Did it idles rough & runs poorly? Your fuel filter could be clogged. You should hook up a scanner & check for code(s) then report back.
02-21-2019, 12:28 AM
#14
If you're getting fuel pressure & the car fired up then the pump is working so your issue isn't the same as mine. Did you get a reading of the fuel pressure & what's it? How was the car running before? Did it idles rough & runs poorly? Your fuel filter could be clogged. You should hook up a scanner & check for code(s) then report back.
02-21-2019, 12:41 AM
#15
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The filter is integrated in the fuel sending unit on the left side & in order to remove the assembly, you'll need to open up the other side to disconnect the electrical harnesses, fuel hoses & all that so might as well replace the pump at the same time. Being 14 years old, the pump is running on borrowed time & could go anytime. I strongly recommend you should do the whole thing in 1 shot so you won't have to deal with it again.
02-21-2019, 12:55 AM
#16
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Btw, there's a known issue w/ cracked fuel sending unit at the top of the assembly which will spill gas when the system is pressurized. MB kept quiet & didn't issue a service recall but they do extend the warranty to 15 years so if yours haven't been replaced before then take it into an MB dealer, tell them you smell raw gas & demand them to replace both fuel sending unit & fuel pump at no charge. The cost to replace both at the dealer is slightly over $2K. You should thanks me & pay me 10% for the consulting fee. 
Last edited by superfast; 02-21-2019 at 12:58 AM.
02-21-2019, 01:03 AM
#17
Btw, there's a known issue w/ cracked fuel sending unit at the top of the assembly which will spill gas when the system is pressurized. MB kept quiet & didn't issue a service recall but they do extend the warranty to 15 years so if yours haven't been replaced before then take it into an MB dealer, tell them you smell raw gas & demand them to replace both fuel sending unit & fuel pump at no charge. The cost to replace both at the dealer is slightly over $2K. You should thanks me & pay me 10% for the consulting fee.
02-21-2019, 03:51 AM
#18
Hi!
i had similar issue with my 2003 E55 amg. Car behaved just like yours. It was the crankshaftsensor that was faulty. Check yours could be just that and is quite cheap to fix
Arian
i had similar issue with my 2003 E55 amg. Car behaved just like yours. It was the crankshaftsensor that was faulty. Check yours could be just that and is quite cheap to fix
Arian
02-27-2019, 09:48 PM
#19
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Received the new OEM fuel pump & fuel sending unit yesterday & got them replaced this afternoon. The job took 1.5 hour to complete. As expected, car fired right up & runs great.
02-28-2019, 11:08 AM
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'71 Pinto
02-28-2019, 11:18 AM
#21
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Konigstiger- The fuel sending unit has 3 long fuel hoses, size 3/8" to 1/2" in dia. 1 of them is connected to the fuel pump but the other 2 just hanging right next to the pump & not connecting to anything. It's Mercedes Benz's design so I think those 2 hoses are for the overflow but I'm not 100% sure. Any idea?
02-28-2019, 12:55 PM
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'71 Pinto
02-28-2019, 01:24 PM
#23
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I have seen a few "How To" articles from the Pelican website. They're very good articles, however it doesn't mention about the 2 extra fuel hoses but I'm sure my guess is pretty close. Also, do you know why there are 2 floats (1 at the pump & the other at the sending unit)? Is one primary & the other redundant? If not, which one is connected & provided the fuel level telemetry signal to the fuel gauge at the instrument panel? I'm a EE scientist so I'm curious at these things & setups. Thanks.
02-28-2019, 01:30 PM
#24
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Come to think of it, I think 1 is used to control the shutoff valve & the other is connected to the fuel gauge to provide fuel level telemetry. I think I may have answered my own question.
Last edited by superfast; 03-01-2019 at 12:54 AM.
