Helpppp with fuel issue
Thread Starter
TECH Regular
Joined: Aug 2007
Posts: 405
Likes: 42
Helpppp with fuel issue I have a 67 Chevelle with a turbo 5.3. At about 6200rpm my fuel pressure drops down to 43psi on the regulator gauge. Here is my fuel set up.
fuel cell
10an from cell to pre filter, to AEM 380LPH pump to a post filter to a check valve
10an from check valve to the engine compartment. Then it Y’s off into 2 8an feeds that connect to the back of Each fuel rail.
The front of of the driver side rail has the Aeromotive FPR boost referenced attached and the passenger side rail has a 8an crossover tube that attaches to the fpr.
6an return off the regulator to the tank.
I have deka 80lb injectors, ls9 cam. This thing will go to 7k no problem but I noticed after 6200rpm the fp drops from 58 to 42 or 43.
my fuel pump has a chassis ground, and I made sure to grind the metal where the ground is attached. The 12v+ goes from the battery, to a breaker, and to the relay, all the way to the pump. I used 12ga wire.
i didn’t check pump voltage when it was being dyno’d.
Car made 595/513 through a th400 and 9”.
please, any suggestions would be awesome
fuel cell
10an from cell to pre filter, to AEM 380LPH pump to a post filter to a check valve
10an from check valve to the engine compartment. Then it Y’s off into 2 8an feeds that connect to the back of Each fuel rail.
The front of of the driver side rail has the Aeromotive FPR boost referenced attached and the passenger side rail has a 8an crossover tube that attaches to the fpr.
6an return off the regulator to the tank.
I have deka 80lb injectors, ls9 cam. This thing will go to 7k no problem but I noticed after 6200rpm the fp drops from 58 to 42 or 43.
my fuel pump has a chassis ground, and I made sure to grind the metal where the ground is attached. The 12v+ goes from the battery, to a breaker, and to the relay, all the way to the pump. I used 12ga wire.
i didn’t check pump voltage when it was being dyno’d.
Car made 595/513 through a th400 and 9”.
please, any suggestions would be awesome
I echo what Stevie said, and also add to check your voltage. I had a similar issue a while back and found my alternator quit charging after 6k rpm. Swapped to the bigger dr44 alt and all is well. I could see it on my datalogs, system voltage would drop from 13.8 to 12.6 like a light switch at 6k rpms
Thread Starter
TECH Regular
Joined: Aug 2007
Posts: 405
Likes: 42
I echo what Stevie said, and also add to check your voltage. I had a similar issue a while back and found my alternator quit charging after 6k rpm. Swapped to the bigger dr44 alt and all is well. I could see it on my datalogs, system voltage would drop from 13.8 to 12.6 like a light switch at 6k rpms
I was thinking the same thing about the alternator giving out after 6k. As far as the pressure drop and if it’s slow or fast, I was told this by the tuners shop hand. I’m assuming it dropped down quickly but can’t recall exactly what I was told 😳
yeah they tend to quit working around 18,000 alternator rpm in my experience...which with the small 2.5" alt pulley and a truck balancer (7.5") that happens at 6,000 engine rpm.
You can find a larger alt pulley or a smaller crank pulley to get under that 18k rpm.
You can also install the AD244 "large case" truck alt in place of a CS130d or AD130 and supe them up with parts from alternatorparts.com
Personally I had this problem spinning a 4.8l to 7500 rpm last year. My volts at the pumps were dropping to 11.2! A 3.25" alt pulley from a shitbox FWD caddy and shimming the brushes got the rpm I needed, and re wiring with 6ga to the pump relays and then 10ga to the pumps themselves and now they are good 14.5v as high as I care to rev it.
You can find a larger alt pulley or a smaller crank pulley to get under that 18k rpm.
You can also install the AD244 "large case" truck alt in place of a CS130d or AD130 and supe them up with parts from alternatorparts.com
Personally I had this problem spinning a 4.8l to 7500 rpm last year. My volts at the pumps were dropping to 11.2! A 3.25" alt pulley from a shitbox FWD caddy and shimming the brushes got the rpm I needed, and re wiring with 6ga to the pump relays and then 10ga to the pumps themselves and now they are good 14.5v as high as I care to rev it.
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Joined: Nov 2003
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Likes: 185
From: Norn Iron
yeah they tend to quit working around 18,000 alternator rpm in my experience...which with the small 2.5" alt pulley and a truck balancer (7.5") that happens at 6,000 engine rpm.
You can find a larger alt pulley or a smaller crank pulley to get under that 18k rpm.
You can also install the AD244 "large case" truck alt in place of a CS130d or AD130 and supe them up with parts from alternatorparts.com
Personally I had this problem spinning a 4.8l to 7500 rpm last year. My volts at the pumps were dropping to 11.2! A 3.25" alt pulley from a shitbox FWD caddy and shimming the brushes got the rpm I needed, and re wiring with 6ga to the pump relays and then 10ga to the pumps themselves and now they are good 14.5v as high as I care to rev it.
You can find a larger alt pulley or a smaller crank pulley to get under that 18k rpm.
You can also install the AD244 "large case" truck alt in place of a CS130d or AD130 and supe them up with parts from alternatorparts.com
Personally I had this problem spinning a 4.8l to 7500 rpm last year. My volts at the pumps were dropping to 11.2! A 3.25" alt pulley from a shitbox FWD caddy and shimming the brushes got the rpm I needed, and re wiring with 6ga to the pump relays and then 10ga to the pumps themselves and now they are good 14.5v as high as I care to rev it.
On my car...it happened the exact same alternator. One that had worked for a long time with no issues...it even failed and had it repaired locally...few years later it failed again.
Then whatever internal parts they changed during this repair...at almost bang on 6k every time, it stopped charging.
I thought brushes, so checked them, all good, increased tension on the springs...no change.
Tried another alternator I had that was a cheapy replacement....ffs it did the bloody same thing. I did replace the regulator of the original but never got around to trying it again as just said **** that and bought another alternator from these guys and it's been fine since.
https://alternatorparts.com/ad230-ad...ternators.html
